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  1. \input texinfo
  2. @c -*-texinfo-*-
  3. @c %**start of header
  4. @setfilename
  5. @documentencoding UTF-8
  6. @settitle GNU Guix Reference Manual
  7. @c %**end of header
  8. @include version.texi
  9. @copying
  10. Copyright @copyright{} 2012, 2013, 2014, 2015 Ludovic Courtès@*
  11. Copyright @copyright{} 2013, 2014 Andreas Enge@*
  12. Copyright @copyright{} 2013 Nikita Karetnikov@*
  13. Copyright @copyright{} 2015 Mathieu Lirzin@*
  14. Copyright @copyright{} 2014 Pierre-Antoine Rault@*
  15. Copyright @copyright{} 2015 Taylan Ulrich Bayırlı/Kammer
  16. Permission is granted to copy, distribute and/or modify this document
  17. under the terms of the GNU Free Documentation License, Version 1.3 or
  18. any later version published by the Free Software Foundation; with no
  19. Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A
  20. copy of the license is included in the section entitled ``GNU Free
  21. Documentation License''.
  22. @end copying
  23. @dircategory Package management
  24. @direntry
  25. * guix: (guix). Guix, the functional package manager.
  26. * guix package: (guix)Invoking guix package
  27. Managing packages with Guix.
  28. * guix build: (guix)Invoking guix build
  29. Building packages with Guix.
  30. * guix system: (guix)Invoking guix system
  31. Managing the operating system configuration.
  32. @end direntry
  33. @dircategory Software development
  34. @direntry
  35. * guix environment: (guix)Invoking guix environment
  36. Building development environments with Guix.
  37. @end direntry
  38. @titlepage
  39. @title GNU Guix Reference Manual
  40. @subtitle Using the GNU Guix Functional Package Manager
  41. @author Ludovic Courtès
  42. @author Andreas Enge
  43. @author Nikita Karetnikov
  44. @page
  45. @vskip 0pt plus 1filll
  46. Edition @value{EDITION} @*
  47. @value{UPDATED} @*
  48. @insertcopying
  49. @end titlepage
  50. @contents
  51. @c *********************************************************************
  52. @node Top
  53. @top GNU Guix
  54. This document describes GNU Guix version @value{VERSION}, a functional
  55. package management tool written for the GNU system.
  56. @menu
  57. * Introduction:: What is Guix about?
  58. * Installation:: Installing Guix.
  59. * Package Management:: Package installation, upgrade, etc.
  60. * Programming Interface:: Using Guix in Scheme.
  61. * Utilities:: Package management commands.
  62. * GNU Distribution:: Software for your friendly GNU system.
  63. * Contributing:: Your help needed!
  64. * Acknowledgments:: Thanks!
  65. * GNU Free Documentation License:: The license of this manual.
  66. * Concept Index:: Concepts.
  67. * Programming Index:: Data types, functions, and variables.
  68. @detailmenu
  69. --- The Detailed Node Listing ---
  70. Installation
  71. * Binary Installation:: Getting Guix running in no time!
  72. * Requirements:: Software needed to build and run Guix.
  73. * Running the Test Suite:: Testing Guix.
  74. * Setting Up the Daemon:: Preparing the build daemon's environment.
  75. * Invoking guix-daemon:: Running the build daemon.
  76. Setting Up the Daemon
  77. * Build Environment Setup:: Preparing the isolated build environment.
  78. * Daemon Offload Setup:: Offloading builds to remote machines.
  79. Package Management
  80. * Features:: How Guix will make your life brighter.
  81. * Invoking guix package:: Package installation, removal, etc.
  82. * Emacs Interface:: Package management from Emacs.
  83. * Substitutes:: Downloading pre-built binaries.
  84. * Packages with Multiple Outputs:: Single source package, multiple outputs.
  85. * Invoking guix gc:: Running the garbage collector.
  86. * Invoking guix pull:: Fetching the latest Guix and distribution.
  87. * Invoking guix archive:: Exporting and importing store files.
  88. Programming Interface
  89. * Defining Packages:: Defining new packages.
  90. * Build Systems:: Specifying how packages are built.
  91. * The Store:: Manipulating the package store.
  92. * Derivations:: Low-level interface to package derivations.
  93. * The Store Monad:: Purely functional interface to the store.
  94. * G-Expressions:: Manipulating build expressions.
  95. Defining Packages
  96. * package Reference:: The package data type.
  97. * origin Reference:: The origin data type.
  98. Utilities
  99. * Invoking guix build:: Building packages from the command line.
  100. * Invoking guix download:: Downloading a file and printing its hash.
  101. * Invoking guix hash:: Computing the cryptographic hash of a file.
  102. * Invoking guix import:: Importing package definitions.
  103. * Invoking guix refresh:: Updating package definitions.
  104. * Invoking guix lint:: Finding errors in package definitions.
  105. * Invoking guix environment:: Setting up development environments.
  106. * Invoking guix publish:: Sharing substitutes.
  107. GNU Distribution
  108. * System Installation:: Installing the whole operating system.
  109. * System Configuration:: Configuring the operating system.
  110. * Installing Debugging Files:: Feeding the debugger.
  111. * Security Updates:: Deploying security fixes quickly.
  112. * Package Modules:: Packages from the programmer's viewpoint.
  113. * Packaging Guidelines:: Growing the distribution.
  114. * Bootstrapping:: GNU/Linux built from scratch.
  115. * Porting:: Targeting another platform or kernel.
  116. System Configuration
  117. * Using the Configuration System:: Customizing your GNU system.
  118. * operating-system Reference:: Detail of operating-system declarations.
  119. * File Systems:: Configuring file system mounts.
  120. * Mapped Devices:: Block device extra processing.
  121. * User Accounts:: Specifying user accounts.
  122. * Locales:: Language and cultural convention settings.
  123. * Services:: Specifying system services.
  124. * Setuid Programs:: Programs running with root privileges.
  125. * X.509 Certificates:: Authenticating HTTPS servers.
  126. * Name Service Switch:: Configuring libc's name service switch.
  127. * Initial RAM Disk:: Linux-Libre bootstrapping.
  128. * GRUB Configuration:: Configuring the boot loader.
  129. * Invoking guix system:: Instantiating a system configuration.
  130. * Defining Services:: Adding new service definitions.
  131. Services
  132. * Base Services:: Essential system services.
  133. * Networking Services:: Network setup, SSH daemon, etc.
  134. * X Window:: Graphical display.
  135. * Desktop Services:: D-Bus and desktop services.
  136. * Database Services:: SQL databases.
  137. * Various Services:: Other services.
  138. Packaging Guidelines
  139. * Software Freedom:: What may go into the distribution.
  140. * Package Naming:: What's in a name?
  141. * Version Numbers:: When the name is not enough.
  142. * Python Modules:: Taming the snake.
  143. * Perl Modules:: Little pearls.
  144. * Fonts:: Fond of fonts.
  145. Contributing
  146. * Building from Git:: The latest and greatest.
  147. * Running Guix Before It Is Installed:: Hacker tricks.
  148. * The Perfect Setup:: The right tools.
  149. * Coding Style:: Hygiene of the contributor.
  150. * Submitting Patches:: Share your work.
  151. Coding Style
  152. * Programming Paradigm:: How to compose your elements.
  153. * Modules:: Where to store your code?
  154. * Data Types and Pattern Matching:: Implementing data structures.
  155. * Formatting Code:: Writing conventions.
  156. @end detailmenu
  157. @end menu
  158. @c *********************************************************************
  159. @node Introduction
  160. @chapter Introduction
  161. GNU Guix@footnote{``Guix'' is pronounced like ``geeks'', or ``ɡiːks''
  162. using the international phonetic alphabet (IPA).} is a functional
  163. package management tool for the GNU system. Package management consists
  164. of all activities that relate to building packages from sources,
  165. honoring their build-time and run-time dependencies,
  166. installing packages in user environments, upgrading installed packages
  167. to new versions or rolling back to a previous set, removing unused
  168. software packages, etc.
  169. @cindex functional package management
  170. The term @dfn{functional} refers to a specific package management
  171. discipline. In Guix, the package build and installation process is seen
  172. as a function, in the mathematical sense. That function takes inputs,
  173. such as build scripts, a compiler, and libraries, and
  174. returns an installed package. As a pure function, its result depends
  175. solely on its inputs---for instance, it cannot refer to software or
  176. scripts that were not explicitly passed as inputs. A build function
  177. always produces the same result when passed a given set of inputs. It
  178. cannot alter the system's environment in
  179. any way; for instance, it cannot create, modify, or delete files outside
  180. of its build and installation directories. This is achieved by running
  181. build processes in isolated environments (or @dfn{containers}), where only their
  182. explicit inputs are visible.
  183. @cindex store
  184. The result of package build functions is @dfn{cached} in the file
  185. system, in a special directory called @dfn{the store} (@pxref{The
  186. Store}). Each package is installed in a directory of its own, in the
  187. store---by default under @file{/gnu/store}. The directory name contains
  188. a hash of all the inputs used to build that package; thus, changing an
  189. input yields a different directory name.
  190. This approach is the foundation of Guix's salient features: support for
  191. transactional package upgrade and rollback, per-user installation, and
  192. garbage collection of packages (@pxref{Features}).
  193. Guix has a command-line interface, which allows users to build, install,
  194. upgrade, and remove packages, as well as a Scheme programming interface.
  195. @cindex Guix System Distribution
  196. @cindex GuixSD
  197. Last but not least, Guix is used to build a distribution of the GNU
  198. system, with many GNU and non-GNU free software packages. The Guix
  199. System Distribution, or GNU@tie{}GuixSD, takes advantage of the core
  200. properties of Guix at the system level. With GuixSD, users
  201. @emph{declare} all aspects of the operating system configuration, and
  202. Guix takes care of instantiating that configuration in a reproducible,
  203. stateless fashion. @xref{GNU Distribution}.
  204. @c *********************************************************************
  205. @node Installation
  206. @chapter Installation
  207. GNU Guix is available for download from its website at
  208. @url{}. This section describes the
  209. software requirements of Guix, as well as how to install it and get
  210. ready to use it.
  211. Note that this section is concerned with the installation of the package
  212. manager, which can be done on top of a running GNU/Linux system. If,
  213. instead, you want to install the complete GNU operating system,
  214. @pxref{System Installation}.
  215. @menu
  216. * Binary Installation:: Getting Guix running in no time!
  217. * Requirements:: Software needed to build and run Guix.
  218. * Running the Test Suite:: Testing Guix.
  219. * Setting Up the Daemon:: Preparing the build daemon's environment.
  220. * Invoking guix-daemon:: Running the build daemon.
  221. @end menu
  222. @node Binary Installation
  223. @section Binary Installation
  224. This section describes how to install Guix on an arbitrary system from a
  225. self-contained tarball providing binaries for Guix and for all its
  226. dependencies. This is often quicker than installing from source, which
  227. is described in the next sections. The only requirement is to have
  228. GNU@tie{}tar and Xz.
  229. Installing goes along these lines:
  230. @enumerate
  231. @item
  232. Download the binary tarball from
  233. @indicateurl{{VERSION}.@var{system}.tar.xz}@footnote{As
  234. usual, make sure to download the associated @file{.sig} file and to
  235. verify the authenticity of the tarball against it!}, where @var{system}
  236. is @code{x86_64-linux} for an @code{x86_64} machine already running the
  237. kernel Linux, and so on.
  238. @item
  239. As @code{root}, run:
  240. @example
  241. # cd /tmp
  242. # tar xf guix-binary-@value{VERSION}.@var{system}.tar.xz
  243. # mv var/guix /var/ && mv gnu /
  244. @end example
  245. This creates @file{/gnu/store} (@pxref{The Store}) and @file{/var/guix}.
  246. The latter contains a ready-to-use profile for @code{root} (see next
  247. step.)
  248. Do @emph{not} unpack the tarball on a working Guix system since that
  249. would overwrite its own essential files.
  250. @item
  251. Make @code{root}'s profile available under @file{~/.guix-profile}:
  252. @example
  253. # ln -sf /var/guix/profiles/per-user/root/guix-profile \
  254. ~root/.guix-profile
  255. @end example
  256. @item
  257. Run the daemon:
  258. @example
  259. # ~root/.guix-profile/bin/guix-daemon --build-users-group=guixbuild
  260. @end example
  261. @item
  262. Make the @command{guix} command available to other users on the machine,
  263. for instance with:
  264. @example
  265. # mkdir -p /usr/local/bin
  266. # cd /usr/local/bin
  267. # ln -s /var/guix/profiles/per-user/root/guix-profile/bin/guix
  268. @end example
  269. @item
  270. To use substitutes from @code{} (@pxref{Substitutes}),
  271. authorize them:
  272. @example
  273. # guix archive --authorize < ~root/.guix-profile/share/guix/
  274. @end example
  275. @end enumerate
  276. And that's it!
  277. The @code{guix} package must remain available in @code{root}'s
  278. profile, or it would become subject to garbage collection---in which
  279. case you would find yourself badly handicapped by the lack of the
  280. @command{guix} command.
  281. The tarball in question can be (re)produced and verified simply by
  282. running the following command in the Guix source tree:
  283. @example
  284. make guix-binary.@var{system}.tar.xz
  285. @end example
  286. @node Requirements
  287. @section Requirements
  288. This section lists requirements when building Guix from source. The
  289. build procedure for Guix is the same as for other GNU software, and is
  290. not covered here. Please see the files @file{README} and @file{INSTALL}
  291. in the Guix source tree for additional details.
  292. GNU Guix depends on the following packages:
  293. @itemize
  294. @item @url{, GNU Guile}, version 2.0.7 or later;
  295. @item @url{, GNU libgcrypt};
  296. @item @url{, GNU Make}.
  297. @end itemize
  298. The following dependencies are optional:
  299. @itemize
  300. @item
  301. Installing
  302. @url{, Guile-JSON} will
  303. allow you to use the @command{guix import pypi} command (@pxref{Invoking
  304. guix import}). It is of
  305. interest primarily for developers and not for casual users.
  306. @item
  307. Installing @uref{, GnuTLS-Guile} will
  308. allow you to access @code{https} URLs with the @command{guix download}
  309. command (@pxref{Invoking guix download}), the @command{guix import pypi}
  310. command, and the @command{guix import cpan} command. This is primarily
  311. of interest to developers. @xref{Guile Preparations, how to install the
  312. GnuTLS bindings for Guile,, gnutls-guile, GnuTLS-Guile}.
  313. @end itemize
  314. Unless @code{--disable-daemon} was passed to @command{configure}, the
  315. following packages are also needed:
  316. @itemize
  317. @item @url{, SQLite 3};
  318. @item @url{, libbz2};
  319. @item @url{, GCC's g++}, with support for the
  320. C++11 standard.
  321. @end itemize
  322. When a working installation of @url{, the Nix package
  323. manager} is available, you
  324. can instead configure Guix with @code{--disable-daemon}. In that case,
  325. Nix replaces the three dependencies above.
  326. Guix is compatible with Nix, so it is possible to share the same store
  327. between both. To do so, you must pass @command{configure} not only the
  328. same @code{--with-store-dir} value, but also the same
  329. @code{--localstatedir} value. The latter is essential because it
  330. specifies where the database that stores metadata about the store is
  331. located, among other things. The default values for Nix are
  332. @code{--with-store-dir=/nix/store} and @code{--localstatedir=/nix/var}.
  333. Note that @code{--disable-daemon} is not required if
  334. your goal is to share the store with Nix.
  335. @node Running the Test Suite
  336. @section Running the Test Suite
  337. After a successful @command{configure} and @code{make} run, it is a good
  338. idea to run the test suite. It can help catch issues with the setup or
  339. environment, or bugs in Guix itself---and really, reporting test
  340. failures is a good way to help improve the software. To run the test
  341. suite, type:
  342. @example
  343. make check
  344. @end example
  345. Test cases can run in parallel: you can use the @code{-j} option of
  346. GNU@tie{}make to speed things up. The first run may take a few minutes
  347. on a recent machine; subsequent runs will be faster because the store
  348. that is created for test purposes will already have various things in
  349. cache.
  350. Upon failure, please email @email{} and attach the
  351. @file{test-suite.log} file. When @file{tests/@var{something}.scm}
  352. fails, please also attach the @file{@var{something}.log} file available
  353. in the top-level build directory. Please specify the Guix version being
  354. used as well as version numbers of the dependencies
  355. (@pxref{Requirements}) in your message.
  356. @node Setting Up the Daemon
  357. @section Setting Up the Daemon
  358. @cindex daemon
  359. Operations such as building a package or running the garbage collector
  360. are all performed by a specialized process, the @dfn{build daemon}, on
  361. behalf of clients. Only the daemon may access the store and its
  362. associated database. Thus, any operation that manipulates the store
  363. goes through the daemon. For instance, command-line tools such as
  364. @command{guix package} and @command{guix build} communicate with the
  365. daemon (@i{via} remote procedure calls) to instruct it what to do.
  366. The following sections explain how to prepare the build daemon's
  367. environment. Also @ref{Substitutes}, for information on how to allow
  368. the daemon to download pre-built binaries.
  369. @menu
  370. * Build Environment Setup:: Preparing the isolated build environment.
  371. * Daemon Offload Setup:: Offloading builds to remote machines.
  372. @end menu
  373. @node Build Environment Setup
  374. @subsection Build Environment Setup
  375. In a standard multi-user setup, Guix and its daemon---the
  376. @command{guix-daemon} program---are installed by the system
  377. administrator; @file{/gnu/store} is owned by @code{root} and
  378. @command{guix-daemon} runs as @code{root}. Unprivileged users may use
  379. Guix tools to build packages or otherwise access the store, and the
  380. daemon will do it on their behalf, ensuring that the store is kept in a
  381. consistent state, and allowing built packages to be shared among users.
  382. @cindex build users
  383. When @command{guix-daemon} runs as @code{root}, you may not want package
  384. build processes themselves to run as @code{root} too, for obvious
  385. security reasons. To avoid that, a special pool of @dfn{build users}
  386. should be created for use by build processes started by the daemon.
  387. These build users need not have a shell and a home directory: they will
  388. just be used when the daemon drops @code{root} privileges in build
  389. processes. Having several such users allows the daemon to launch
  390. distinct build processes under separate UIDs, which guarantees that they
  391. do not interfere with each other---an essential feature since builds are
  392. regarded as pure functions (@pxref{Introduction}).
  393. On a GNU/Linux system, a build user pool may be created like this (using
  394. Bash syntax and the @code{shadow} commands):
  395. @c See
  396. @c for why `-G' is needed.
  397. @example
  398. # groupadd --system guixbuild
  399. # for i in `seq -w 1 10`;
  400. do
  401. useradd -g guixbuild -G guixbuild \
  402. -d /var/empty -s `which nologin` \
  403. -c "Guix build user $i" --system \
  404. guixbuilder$i;
  405. done
  406. @end example
  407. @noindent
  408. The number of build users determines how many build jobs may run in
  409. parallel, as specified by the @option{--max-jobs} option
  410. (@pxref{Invoking guix-daemon, @option{--max-jobs}}).
  411. The @code{guix-daemon} program may then be run as @code{root} with:
  412. @example
  413. # guix-daemon --build-users-group=guixbuild
  414. @end example
  415. @cindex chroot
  416. @noindent
  417. This way, the daemon starts build processes in a chroot, under one of
  418. the @code{guixbuilder} users. On GNU/Linux, by default, the chroot
  419. environment contains nothing but:
  420. @c Keep this list in sync with libstore/! -----------------------
  421. @itemize
  422. @item
  423. a minimal @code{/dev} directory, created mostly independently from the
  424. host @code{/dev}@footnote{``Mostly'', because while the set of files
  425. that appear in the chroot's @code{/dev} is fixed, most of these files
  426. can only be created if the host has them.};
  427. @item
  428. the @code{/proc} directory; it only shows the container's processes
  429. since a separate PID name space is used;
  430. @item
  431. @file{/etc/passwd} with an entry for the current user and an entry for
  432. user @file{nobody};
  433. @item
  434. @file{/etc/group} with an entry for the user's group;
  435. @item
  436. @file{/etc/hosts} with an entry that maps @code{localhost} to
  437. @code{};
  438. @item
  439. a writable @file{/tmp} directory.
  440. @end itemize
  441. If you are installing Guix as an unprivileged user, it is still possible
  442. to run @command{guix-daemon} provided you pass @code{--disable-chroot}.
  443. However, build processes will not be isolated from one another, and not
  444. from the rest of the system. Thus, build processes may interfere with
  445. each other, and may access programs, libraries, and other files
  446. available on the system---making it much harder to view them as
  447. @emph{pure} functions.
  448. @node Daemon Offload Setup
  449. @subsection Using the Offload Facility
  450. @cindex offloading
  451. @cindex build hook
  452. When desired, the build daemon can @dfn{offload}
  453. derivation builds to other machines
  454. running Guix, using the @code{offload} @dfn{build hook}. When that
  455. feature is enabled, a list of user-specified build machines is read from
  456. @file{/etc/guix/machines.scm}; anytime a build is requested, for
  457. instance via @code{guix build}, the daemon attempts to offload it to one
  458. of the machines that satisfies the derivation's constraints, in
  459. particular its system type---e.g., @file{x86_64-linux}. Missing
  460. prerequisites for the build are copied over SSH to the target machine,
  461. which then proceeds with the build; upon success the output(s) of the
  462. build are copied back to the initial machine.
  463. The @file{/etc/guix/machines.scm} file typically looks like this:
  464. @example
  465. (list (build-machine
  466. (name "")
  467. (system "x86_64-linux")
  468. (user "bob")
  469. (speed 2.)) ; incredibly fast!
  470. (build-machine
  471. (name "")
  472. (system "mips64el-linux")
  473. (user "alice")
  474. (private-key
  475. (string-append (getenv "HOME")
  476. "/.ssh/id-rsa-for-guix"))))
  477. @end example
  478. @noindent
  479. In the example above we specify a list of two build machines, one for
  480. the @code{x86_64} architecture and one for the @code{mips64el}
  481. architecture.
  482. In fact, this file is---not surprisingly!---a Scheme file that is
  483. evaluated when the @code{offload} hook is started. Its return value
  484. must be a list of @code{build-machine} objects. While this example
  485. shows a fixed list of build machines, one could imagine, say, using
  486. DNS-SD to return a list of potential build machines discovered in the
  487. local network (@pxref{Introduction, Guile-Avahi,, guile-avahi, Using
  488. Avahi in Guile Scheme Programs}). The @code{build-machine} data type is
  489. detailed below.
  490. @deftp {Data Type} build-machine
  491. This data type represents build machines the daemon may offload builds
  492. to. The important fields are:
  493. @table @code
  494. @item name
  495. The remote machine's host name.
  496. @item system
  497. The remote machine's system type---e.g., @code{"x86_64-linux"}.
  498. @item user
  499. The user account to use when connecting to the remote machine over SSH.
  500. Note that the SSH key pair must @emph{not} be passphrase-protected, to
  501. allow non-interactive logins.
  502. @end table
  503. A number of optional fields may be specified:
  504. @table @code
  505. @item port
  506. Port number of the machine's SSH server (default: 22).
  507. @item private-key
  508. The SSH private key file to use when connecting to the machine.
  509. @item parallel-builds
  510. The number of builds that may run in parallel on the machine (1 by
  511. default.)
  512. @item speed
  513. A ``relative speed factor''. The offload scheduler will tend to prefer
  514. machines with a higher speed factor.
  515. @item features
  516. A list of strings denoting specific features supported by the machine.
  517. An example is @code{"kvm"} for machines that have the KVM Linux modules
  518. and corresponding hardware support. Derivations can request features by
  519. name, and they will be scheduled on matching build machines.
  520. @end table
  521. @end deftp
  522. The @code{guix} command must be in the search path on the build
  523. machines, since offloading works by invoking the @code{guix archive} and
  524. @code{guix build} commands.
  525. There's one last thing to do once @file{machines.scm} is in place. As
  526. explained above, when offloading, files are transferred back and forth
  527. between the machine stores. For this to work, you need to generate a
  528. key pair to allow the daemon to export signed archives of files from the
  529. store (@pxref{Invoking guix archive}):
  530. @example
  531. # guix archive --generate-key
  532. @end example
  533. @noindent
  534. Thus, when receiving files, a machine's build daemon can make sure they
  535. are genuine, have not been tampered with, and that they are signed by an
  536. authorized key.
  537. @node Invoking guix-daemon
  538. @section Invoking @command{guix-daemon}
  539. The @command{guix-daemon} program implements all the functionality to
  540. access the store. This includes launching build processes, running the
  541. garbage collector, querying the availability of a build result, etc. It
  542. is normally run as @code{root} like this:
  543. @example
  544. # guix-daemon --build-users-group=guixbuild
  545. @end example
  546. @noindent
  547. For details on how to set it up, @pxref{Setting Up the Daemon}.
  548. @cindex chroot
  549. @cindex container, build environment
  550. @cindex build environment
  551. @cindex reproducible builds
  552. By default, @command{guix-daemon} launches build processes under
  553. different UIDs, taken from the build group specified with
  554. @code{--build-users-group}. In addition, each build process is run in a
  555. chroot environment that only contains the subset of the store that the
  556. build process depends on, as specified by its derivation
  557. (@pxref{Programming Interface, derivation}), plus a set of specific
  558. system directories. By default, the latter contains @file{/dev} and
  559. @file{/dev/pts}. Furthermore, on GNU/Linux, the build environment is a
  560. @dfn{container}: in addition to having its own file system tree, it has
  561. a separate mount name space, its own PID name space, network name space,
  562. etc. This helps achieve reproducible builds (@pxref{Features}).
  563. When the daemon performs a build on behalf of the user, it creates a
  564. build directory under @file{/tmp} or under the directory specified by
  565. its @code{TMPDIR} environment variable; this directory is shared with
  566. the container for the duration of the build. Be aware that using a
  567. directory other than @file{/tmp} can affect build results---for example,
  568. with a longer directory name, a build process that uses Unix-domain
  569. sockets might hit the name length limitation for @code{sun_path}, which
  570. it would otherwise not hit.
  571. The build directory is automatically deleted upon completion, unless the
  572. build failed and the client specified @option{--keep-failed}
  573. (@pxref{Invoking guix build, @option{--keep-failed}}).
  574. The following command-line options are supported:
  575. @table @code
  576. @item --build-users-group=@var{group}
  577. Take users from @var{group} to run build processes (@pxref{Setting Up
  578. the Daemon, build users}).
  579. @item --no-substitutes
  580. @cindex substitutes
  581. Do not use substitutes for build products. That is, always build things
  582. locally instead of allowing downloads of pre-built binaries
  583. (@pxref{Substitutes}).
  584. By default substitutes are used, unless the client---such as the
  585. @command{guix package} command---is explicitly invoked with
  586. @code{--no-substitutes}.
  587. When the daemon runs with @code{--no-substitutes}, clients can still
  588. explicitly enable substitution @i{via} the @code{set-build-options}
  589. remote procedure call (@pxref{The Store}).
  590. @item --substitute-urls=@var{urls}
  591. Consider @var{urls} the default whitespace-separated list of substitute
  592. source URLs. When this option is omitted, @indicateurl{}
  593. is used.
  594. This means that substitutes may be downloaded from @var{urls}, as long
  595. as they are signed by a trusted signature (@pxref{Substitutes}).
  596. @cindex build hook
  597. @item --no-build-hook
  598. Do not use the @dfn{build hook}.
  599. The build hook is a helper program that the daemon can start and to
  600. which it submits build requests. This mechanism is used to offload
  601. builds to other machines (@pxref{Daemon Offload Setup}).
  602. @item --cache-failures
  603. Cache build failures. By default, only successful builds are cached.
  604. @item --cores=@var{n}
  605. @itemx -c @var{n}
  606. Use @var{n} CPU cores to build each derivation; @code{0} means as many
  607. as available.
  608. The default value is @code{0}, but it may be overridden by clients, such
  609. as the @code{--cores} option of @command{guix build} (@pxref{Invoking
  610. guix build}).
  611. The effect is to define the @code{NIX_BUILD_CORES} environment variable
  612. in the build process, which can then use it to exploit internal
  613. parallelism---for instance, by running @code{make -j$NIX_BUILD_CORES}.
  614. @item --max-jobs=@var{n}
  615. @itemx -M @var{n}
  616. Allow at most @var{n} build jobs in parallel. The default value is
  617. @code{1}. Setting it to @code{0} means that no builds will be performed
  618. locally; instead, the daemon will offload builds (@pxref{Daemon Offload
  619. Setup}), or simply fail.
  620. @item --debug
  621. Produce debugging output.
  622. This is useful to debug daemon start-up issues, but then it may be
  623. overridden by clients, for example the @code{--verbosity} option of
  624. @command{guix build} (@pxref{Invoking guix build}).
  625. @item --chroot-directory=@var{dir}
  626. Add @var{dir} to the build chroot.
  627. Doing this may change the result of build processes---for instance if
  628. they use optional dependencies found in @var{dir} when it is available,
  629. and not otherwise. For that reason, it is not recommended to do so.
  630. Instead, make sure that each derivation declares all the inputs that it
  631. needs.
  632. @item --disable-chroot
  633. Disable chroot builds.
  634. Using this option is not recommended since, again, it would allow build
  635. processes to gain access to undeclared dependencies. It is necessary,
  636. though, when @command{guix-daemon} is running under an unprivileged user
  637. account.
  638. @item --disable-log-compression
  639. Disable compression of the build logs.
  640. Unless @code{--lose-logs} is used, all the build logs are kept in the
  641. @var{localstatedir}. To save space, the daemon automatically compresses
  642. them with bzip2 by default. This option disables that.
  643. @item --disable-deduplication
  644. @cindex deduplication
  645. Disable automatic file ``deduplication'' in the store.
  646. By default, files added to the store are automatically ``deduplicated'':
  647. if a newly added file is identical to another one found in the store,
  648. the daemon makes the new file a hard link to the other file. This can
  649. noticeably reduce disk usage, at the expense of slightly increasde
  650. input/output load at the end of a build process. This option disables
  651. this optimization.
  652. @item --gc-keep-outputs[=yes|no]
  653. Tell whether the garbage collector (GC) must keep outputs of live
  654. derivations.
  655. When set to ``yes'', the GC will keep the outputs of any live derivation
  656. available in the store---the @code{.drv} files. The default is ``no'',
  657. meaning that derivation outputs are kept only if they are GC roots.
  658. @item --gc-keep-derivations[=yes|no]
  659. Tell whether the garbage collector (GC) must keep derivations
  660. corresponding to live outputs.
  661. When set to ``yes'', as is the case by default, the GC keeps
  662. derivations---i.e., @code{.drv} files---as long as at least one of their
  663. outputs is live. This allows users to keep track of the origins of
  664. items in their store. Setting it to ``no'' saves a bit of disk space.
  665. Note that when both @code{--gc-keep-derivations} and
  666. @code{--gc-keep-outputs} are used, the effect is to keep all the build
  667. prerequisites (the sources, compiler, libraries, and other build-time
  668. tools) of live objects in the store, regardless of whether these
  669. prerequisites are live. This is convenient for developers since it
  670. saves rebuilds or downloads.
  671. @item --impersonate-linux-2.6
  672. On Linux-based systems, impersonate Linux 2.6. This means that the
  673. kernel's @code{uname} system call will report 2.6 as the release number.
  674. This might be helpful to build programs that (usually wrongfully) depend
  675. on the kernel version number.
  676. @item --lose-logs
  677. Do not keep build logs. By default they are kept under
  678. @code{@var{localstatedir}/guix/log}.
  679. @item --system=@var{system}
  680. Assume @var{system} as the current system type. By default it is the
  681. architecture/kernel pair found at configure time, such as
  682. @code{x86_64-linux}.
  683. @item --listen=@var{socket}
  684. Listen for connections on @var{socket}, the file name of a Unix-domain
  685. socket. The default socket is
  686. @file{@var{localstatedir}/daemon-socket/socket}. This option is only
  687. useful in exceptional circumstances, such as if you need to run several
  688. daemons on the same machine.
  689. @end table
  690. @c *********************************************************************
  691. @node Package Management
  692. @chapter Package Management
  693. The purpose of GNU Guix is to allow users to easily install, upgrade, and
  694. remove software packages, without having to know about their build
  695. procedure or dependencies. Guix also goes beyond this obvious set of
  696. features.
  697. This chapter describes the main features of Guix, as well as the package
  698. management tools it provides. Two user interfaces are provided for
  699. routine package management tasks: a command-line interface
  700. (@pxref{Invoking guix package, @code{guix package}}), and a visual user
  701. interface in Emacs (@pxref{Emacs Interface}).
  702. @menu
  703. * Features:: How Guix will make your life brighter.
  704. * Invoking guix package:: Package installation, removal, etc.
  705. * Emacs Interface:: Package management from Emacs.
  706. * Substitutes:: Downloading pre-built binaries.
  707. * Packages with Multiple Outputs:: Single source package, multiple outputs.
  708. * Invoking guix gc:: Running the garbage collector.
  709. * Invoking guix pull:: Fetching the latest Guix and distribution.
  710. * Invoking guix archive:: Exporting and importing store files.
  711. @end menu
  712. @node Features
  713. @section Features
  714. When using Guix, each package ends up in the @dfn{package store}, in its
  715. own directory---something that resembles
  716. @file{/gnu/store/xxx-package-1.2}, where @code{xxx} is a base32 string
  717. (note that Guix comes with an Emacs extension to shorten those file
  718. names, @pxref{Emacs Prettify}.)
  719. Instead of referring to these directories, users have their own
  720. @dfn{profile}, which points to the packages that they actually want to
  721. use. These profiles are stored within each user's home directory, at
  722. @code{$HOME/.guix-profile}.
  723. For example, @code{alice} installs GCC 4.7.2. As a result,
  724. @file{/home/alice/.guix-profile/bin/gcc} points to
  725. @file{/gnu/store/@dots{}-gcc-4.7.2/bin/gcc}. Now, on the same machine,
  726. @code{bob} had already installed GCC 4.8.0. The profile of @code{bob}
  727. simply continues to point to
  728. @file{/gnu/store/@dots{}-gcc-4.8.0/bin/gcc}---i.e., both versions of GCC
  729. coexist on the same system without any interference.
  730. The @command{guix package} command is the central tool to manage
  731. packages (@pxref{Invoking guix package}). It operates on those per-user
  732. profiles, and can be used @emph{with normal user privileges}.
  733. The command provides the obvious install, remove, and upgrade
  734. operations. Each invocation is actually a @emph{transaction}: either
  735. the specified operation succeeds, or nothing happens. Thus, if the
  736. @command{guix package} process is terminated during the transaction,
  737. or if a power outage occurs during the transaction, then the user's
  738. profile remains in its previous state, and remains usable.
  739. In addition, any package transaction may be @emph{rolled back}. So, if,
  740. for example, an upgrade installs a new version of a package that turns
  741. out to have a serious bug, users may roll back to the previous instance
  742. of their profile, which was known to work well. Similarly, the global
  743. system configuration is subject to transactional upgrades and roll-back
  744. (@pxref{Using the Configuration System}).
  745. All those packages in the package store may be @emph{garbage-collected}.
  746. Guix can determine which packages are still referenced by the user
  747. profiles, and remove those that are provably no longer referenced
  748. (@pxref{Invoking guix gc}). Users may also explicitly remove old
  749. generations of their profile so that the packages they refer to can be
  750. collected.
  751. @cindex reproducibility
  752. @cindex reproducible builds
  753. Finally, Guix takes a @dfn{purely functional} approach to package
  754. management, as described in the introduction (@pxref{Introduction}).
  755. Each @file{/gnu/store} package directory name contains a hash of all the
  756. inputs that were used to build that package---compiler, libraries, build
  757. scripts, etc. This direct correspondence allows users to make sure a
  758. given package installation matches the current state of their
  759. distribution. It also helps maximize @dfn{build reproducibility}:
  760. thanks to the isolated build environments that are used, a given build
  761. is likely to yield bit-identical files when performed on different
  762. machines (@pxref{Invoking guix-daemon, container}).
  763. @cindex substitutes
  764. This foundation allows Guix to support @dfn{transparent binary/source
  765. deployment}. When a pre-built binary for a @file{/gnu/store} item is
  766. available from an external source---a @dfn{substitute}, Guix just
  767. downloads it and unpacks it;
  768. otherwise, it builds the package from source, locally
  769. (@pxref{Substitutes}).
  770. Control over the build environment is a feature that is also useful for
  771. developers. The @command{guix environment} command allows developers of
  772. a package to quickly set up the right development environment for their
  773. package, without having to manually install the package's dependencies
  774. in their profile (@pxref{Invoking guix environment}).
  775. @node Invoking guix package
  776. @section Invoking @command{guix package}
  777. The @command{guix package} command is the tool that allows users to
  778. install, upgrade, and remove packages, as well as rolling back to
  779. previous configurations. It operates only on the user's own profile,
  780. and works with normal user privileges (@pxref{Features}). Its syntax
  781. is:
  782. @example
  783. guix package @var{options}
  784. @end example
  785. Primarily, @var{options} specifies the operations to be performed during
  786. the transaction. Upon completion, a new profile is created, but
  787. previous @dfn{generations} of the profile remain available, should the user
  788. want to roll back.
  789. For example, to remove @code{lua} and install @code{guile} and
  790. @code{guile-cairo} in a single transaction:
  791. @example
  792. guix package -r lua -i guile guile-cairo
  793. @end example
  794. @command{guix package} also supports a @dfn{declarative approach}
  795. whereby the user specifies the exact set of packages to be available and
  796. passes it @i{via} the @option{--manifest} option
  797. (@pxref{profile-manifest, @option{--manifest}}).
  798. For each user, a symlink to the user's default profile is automatically
  799. created in @file{$HOME/.guix-profile}. This symlink always points to the
  800. current generation of the user's default profile. Thus, users can add
  801. @file{$HOME/.guix-profile/bin} to their @code{PATH} environment
  802. variable, and so on.
  803. @cindex search paths
  804. If you are not using the Guix System Distribution, consider adding the
  805. following lines to your @file{~/.bash_profile} (@pxref{Bash Startup
  806. Files,,, bash, The GNU Bash Reference Manual}) so that newly-spawned
  807. shells get all the right environment variable definitions:
  808. @example
  809. GUIX_PROFILE="$HOME/.guix-profile" \
  810. source "$HOME/.guix-profile/etc/profile"
  811. @end example
  812. In a multi-user setup, user profiles are stored in a place registered as
  813. a @dfn{garbage-collector root}, which @file{$HOME/.guix-profile} points
  814. to (@pxref{Invoking guix gc}). That directory is normally
  815. @code{@var{localstatedir}/profiles/per-user/@var{user}}, where
  816. @var{localstatedir} is the value passed to @code{configure} as
  817. @code{--localstatedir}, and @var{user} is the user name. The
  818. @file{per-user} directory is created when @command{guix-daemon} is
  819. started, and the @var{user} sub-directory is created by @command{guix
  820. package}.
  821. The @var{options} can be among the following:
  822. @table @code
  823. @item --install=@var{package} @dots{}
  824. @itemx -i @var{package} @dots{}
  825. Install the specified @var{package}s.
  826. Each @var{package} may specify either a simple package name, such as
  827. @code{guile}, or a package name followed by a hyphen and version number,
  828. such as @code{guile-1.8.8} or simply @code{guile-1.8} (in the latter
  829. case, the newest version prefixed by @code{1.8} is selected.)
  830. If no version number is specified, the
  831. newest available version will be selected. In addition, @var{package}
  832. may contain a colon, followed by the name of one of the outputs of the
  833. package, as in @code{gcc:doc} or @code{binutils-2.22:lib}
  834. (@pxref{Packages with Multiple Outputs}). Packages with a corresponding
  835. name (and optionally version) are searched for among the GNU
  836. distribution modules (@pxref{Package Modules}).
  837. @cindex propagated inputs
  838. Sometimes packages have @dfn{propagated inputs}: these are dependencies
  839. that automatically get installed along with the required package
  840. (@pxref{package-propagated-inputs, @code{propagated-inputs} in
  841. @code{package} objects}, for information about propagated inputs in
  842. package definitions).
  843. @anchor{package-cmd-propagated-inputs}
  844. An example is the GNU MPC library: its C header files refer to those of
  845. the GNU MPFR library, which in turn refer to those of the GMP library.
  846. Thus, when installing MPC, the MPFR and GMP libraries also get installed
  847. in the profile; removing MPC also removes MPFR and GMP---unless they had
  848. also been explicitly installed independently.
  849. Besides, packages sometimes rely on the definition of environment
  850. variables for their search paths (see explanation of
  851. @code{--search-paths} below). Any missing or possibly incorrect
  852. environment variable definitions are reported here.
  853. @c XXX: keep me up-to-date
  854. Finally, when installing a GNU package, the tool reports the
  855. availability of a newer upstream version. In the future, it may provide
  856. the option of installing directly from the upstream version, even if
  857. that version is not yet in the distribution.
  858. @item --install-from-expression=@var{exp}
  859. @itemx -e @var{exp}
  860. Install the package @var{exp} evaluates to.
  861. @var{exp} must be a Scheme expression that evaluates to a
  862. @code{<package>} object. This option is notably useful to disambiguate
  863. between same-named variants of a package, with expressions such as
  864. @code{(@@ (gnu packages base) guile-final)}.
  865. Note that this option installs the first output of the specified
  866. package, which may be insufficient when needing a specific output of a
  867. multiple-output package.
  868. @item --remove=@var{package} @dots{}
  869. @itemx -r @var{package} @dots{}
  870. Remove the specified @var{package}s.
  871. As for @code{--install}, each @var{package} may specify a version number
  872. and/or output name in addition to the package name. For instance,
  873. @code{-r glibc:debug} would remove the @code{debug} output of
  874. @code{glibc}.
  875. @item --upgrade[=@var{regexp} @dots{}]
  876. @itemx -u [@var{regexp} @dots{}]
  877. Upgrade all the installed packages. If one or more @var{regexp}s are
  878. specified, upgrade only installed packages whose name matches a
  879. @var{regexp}. Also see the @code{--do-not-upgrade} option below.
  880. Note that this upgrades package to the latest version of packages found
  881. in the distribution currently installed. To update your distribution,
  882. you should regularly run @command{guix pull} (@pxref{Invoking guix
  883. pull}).
  884. @item --do-not-upgrade[=@var{regexp} @dots{}]
  885. When used together with the @code{--upgrade} option, do @emph{not}
  886. upgrade any packages whose name matches a @var{regexp}. For example, to
  887. upgrade all packages in the current profile except those containing the
  888. substring ``emacs'':
  889. @example
  890. $ guix package --upgrade . --do-not-upgrade emacs
  891. @end example
  892. @item @anchor{profile-manifest}--manifest=@var{file}
  893. @itemx -m @var{file}
  894. @cindex profile declaration
  895. @cindex profile manifest
  896. Create a new generation of the profile from the manifest object
  897. returned by the Scheme code in @var{file}.
  898. This allows you to @emph{declare} the profile's contents rather than
  899. constructing it through a sequence of @code{--install} and similar
  900. commands. The advantage is that @var{file} can be put under version
  901. control, copied to different machines to reproduce the same profile, and
  902. so on.
  903. @c FIXME: Add reference to (guix profile) documentation when available.
  904. @var{file} must return a @dfn{manifest} object, which is roughly a list
  905. of packages:
  906. @findex packages->manifest
  907. @example
  908. (use-package-modules guile emacs)
  909. (packages->manifest
  910. (list emacs
  911. guile-2.0
  912. ;; Use a specific package output.
  913. (list guile-2.0 "debug")))
  914. @end example
  915. @item --roll-back
  916. Roll back to the previous @dfn{generation} of the profile---i.e., undo
  917. the last transaction.
  918. When combined with options such as @code{--install}, roll back occurs
  919. before any other actions.
  920. When rolling back from the first generation that actually contains
  921. installed packages, the profile is made to point to the @dfn{zeroth
  922. generation}, which contains no files apart from its own meta-data.
  923. Installing, removing, or upgrading packages from a generation that has
  924. been rolled back to overwrites previous future generations. Thus, the
  925. history of a profile's generations is always linear.
  926. @item --switch-generation=@var{pattern}
  927. @itemx -S @var{pattern}
  928. Switch to a particular generation defined by @var{pattern}.
  929. @var{pattern} may be either a generation number or a number prefixed
  930. with ``+'' or ``-''. The latter means: move forward/backward by a
  931. specified number of generations. For example, if you want to return to
  932. the latest generation after @code{--roll-back}, use
  933. @code{--switch-generation=+1}.
  934. The difference between @code{--roll-back} and
  935. @code{--switch-generation=-1} is that @code{--switch-generation} will
  936. not make a zeroth generation, so if a specified generation does not
  937. exist, the current generation will not be changed.
  938. @item --search-paths[=@var{kind}]
  939. @cindex search paths
  940. Report environment variable definitions, in Bash syntax, that may be
  941. needed in order to use the set of installed packages. These environment
  942. variables are used to specify @dfn{search paths} for files used by some
  943. of the installed packages.
  944. For example, GCC needs the @code{CPATH} and @code{LIBRARY_PATH}
  945. environment variables to be defined so it can look for headers and
  946. libraries in the user's profile (@pxref{Environment Variables,,, gcc,
  947. Using the GNU Compiler Collection (GCC)}). If GCC and, say, the C
  948. library are installed in the profile, then @code{--search-paths} will
  949. suggest setting these variables to @code{@var{profile}/include} and
  950. @code{@var{profile}/lib}, respectively.
  951. The typical use case is to define these environment variables in the
  952. shell:
  953. @example
  954. $ eval `guix package --search-paths`
  955. @end example
  956. @var{kind} may be one of @code{exact}, @code{prefix}, or @code{suffix},
  957. meaning that the returned environment variable definitions will either
  958. be exact settings, or prefixes or suffixes of the current value of these
  959. variables. When omitted, @var{kind} defaults to @code{exact}.
  960. @item --profile=@var{profile}
  961. @itemx -p @var{profile}
  962. Use @var{profile} instead of the user's default profile.
  963. @item --verbose
  964. Produce verbose output. In particular, emit the environment's build log
  965. on the standard error port.
  966. @item --bootstrap
  967. Use the bootstrap Guile to build the profile. This option is only
  968. useful to distribution developers.
  969. @end table
  970. In addition to these actions @command{guix package} supports the
  971. following options to query the current state of a profile, or the
  972. availability of packages:
  973. @table @option
  974. @item --search=@var{regexp}
  975. @itemx -s @var{regexp}
  976. List the available packages whose name, synopsis, or description matches
  977. @var{regexp}. Print all the meta-data of matching packages in
  978. @code{recutils} format (@pxref{Top, GNU recutils databases,, recutils,
  979. GNU recutils manual}).
  980. This allows specific fields to be extracted using the @command{recsel}
  981. command, for instance:
  982. @example
  983. $ guix package -s malloc | recsel -p name,version
  984. name: glibc
  985. version: 2.17
  986. name: libgc
  987. version: 7.2alpha6
  988. @end example
  989. Similarly, to show the name of all the packages available under the
  990. terms of the GNU@tie{}LGPL version 3:
  991. @example
  992. $ guix package -s "" | recsel -p name -e 'license ~ "LGPL 3"'
  993. name: elfutils
  994. name: gmp
  995. @dots{}
  996. @end example
  997. @item --show=@var{package}
  998. Show details about @var{package}, taken from the list of available packages, in
  999. @code{recutils} format (@pxref{Top, GNU recutils databases,, recutils, GNU
  1000. recutils manual}).
  1001. @example
  1002. $ guix package --show=python | recsel -p name,version
  1003. name: python
  1004. version: 2.7.6
  1005. name: python
  1006. version: 3.3.5
  1007. @end example
  1008. You may also specify the full name of a package to only get details about a
  1009. specific version of it:
  1010. @example
  1011. $ guix package --show=python-3.3.5 | recsel -p name,version
  1012. name: python
  1013. version: 3.3.5
  1014. @end example
  1015. @item --list-installed[=@var{regexp}]
  1016. @itemx -I [@var{regexp}]
  1017. List the currently installed packages in the specified profile, with the
  1018. most recently installed packages shown last. When @var{regexp} is
  1019. specified, list only installed packages whose name matches @var{regexp}.
  1020. For each installed package, print the following items, separated by
  1021. tabs: the package name, its version string, the part of the package that
  1022. is installed (for instance, @code{out} for the default output,
  1023. @code{include} for its headers, etc.), and the path of this package in
  1024. the store.
  1025. @item --list-available[=@var{regexp}]
  1026. @itemx -A [@var{regexp}]
  1027. List packages currently available in the distribution for this system
  1028. (@pxref{GNU Distribution}). When @var{regexp} is specified, list only
  1029. installed packages whose name matches @var{regexp}.
  1030. For each package, print the following items separated by tabs: its name,
  1031. its version string, the parts of the package (@pxref{Packages with
  1032. Multiple Outputs}), and the source location of its definition.
  1033. @item --list-generations[=@var{pattern}]
  1034. @itemx -l [@var{pattern}]
  1035. Return a list of generations along with their creation dates; for each
  1036. generation, show the installed packages, with the most recently
  1037. installed packages shown last. Note that the zeroth generation is never
  1038. shown.
  1039. For each installed package, print the following items, separated by
  1040. tabs: the name of a package, its version string, the part of the package
  1041. that is installed (@pxref{Packages with Multiple Outputs}), and the
  1042. location of this package in the store.
  1043. When @var{pattern} is used, the command returns only matching
  1044. generations. Valid patterns include:
  1045. @itemize
  1046. @item @emph{Integers and comma-separated integers}. Both patterns denote
  1047. generation numbers. For instance, @code{--list-generations=1} returns
  1048. the first one.
  1049. And @code{--list-generations=1,8,2} outputs three generations in the
  1050. specified order. Neither spaces nor trailing commas are allowed.
  1051. @item @emph{Ranges}. @code{--list-generations=2..9} prints the
  1052. specified generations and everything in between. Note that the start of
  1053. a range must be lesser than its end.
  1054. It is also possible to omit the endpoint. For example,
  1055. @code{--list-generations=2..}, returns all generations starting from the
  1056. second one.
  1057. @item @emph{Durations}. You can also get the last @emph{N}@tie{}days, weeks,
  1058. or months by passing an integer along with the first letter of the
  1059. duration. For example, @code{--list-generations=20d} lists generations
  1060. that are up to 20 days old.
  1061. @end itemize
  1062. @item --delete-generations[=@var{pattern}]
  1063. @itemx -d [@var{pattern}]
  1064. When @var{pattern} is omitted, delete all generations except the current
  1065. one.
  1066. This command accepts the same patterns as @option{--list-generations}.
  1067. When @var{pattern} is specified, delete the matching generations. When
  1068. @var{pattern} specifies a duration, generations @emph{older} than the
  1069. specified duration match. For instance, @code{--delete-generations=1m}
  1070. deletes generations that are more than one month old.
  1071. If the current generation matches, it is @emph{not} deleted. Also, the
  1072. zeroth generation is never deleted.
  1073. Note that deleting generations prevents roll-back to them.
  1074. Consequently, this command must be used with care.
  1075. @end table
  1076. Finally, since @command{guix package} may actually start build
  1077. processes, it supports all the common build options that @command{guix
  1078. build} supports (@pxref{Invoking guix build, common build options}).
  1079. @include emacs.texi
  1080. @node Substitutes
  1081. @section Substitutes
  1082. @cindex substitutes
  1083. @cindex pre-built binaries
  1084. Guix supports transparent source/binary deployment, which means that it
  1085. can either build things locally, or download pre-built items from a
  1086. server. We call these pre-built items @dfn{substitutes}---they are
  1087. substitutes for local build results. In many cases, downloading a
  1088. substitute is much faster than building things locally.
  1089. Substitutes can be anything resulting from a derivation build
  1090. (@pxref{Derivations}). Of course, in the common case, they are
  1091. pre-built package binaries, but source tarballs, for instance, which
  1092. also result from derivation builds, can be available as substitutes.
  1093. The @code{} server is a front-end to a build farm that
  1094. builds packages from the GNU distribution continuously for some
  1095. architectures, and makes them available as substitutes. This is the
  1096. default source of substitutes; it can be overridden by passing
  1097. @command{guix-daemon} the @code{--substitute-urls} option
  1098. (@pxref{Invoking guix-daemon}).
  1099. @cindex security
  1100. @cindex digital signatures
  1101. To allow Guix to download substitutes from @code{}, you
  1102. must add its public key to the access control list (ACL) of archive
  1103. imports, using the @command{guix archive} command (@pxref{Invoking guix
  1104. archive}). Doing so implies that you trust @code{} to not
  1105. be compromised and to serve genuine substitutes.
  1106. This public key is installed along with Guix, in
  1107. @code{@var{prefix}/share/guix/}, where @var{prefix} is
  1108. the installation prefix of Guix. If you installed Guix from source,
  1109. make sure you checked the GPG signature of
  1110. @file{guix-@value{VERSION}.tar.gz}, which contains this public key file.
  1111. Then, you can run something like this:
  1112. @example
  1113. # guix archive --authorize <
  1114. @end example
  1115. Once this is in place, the output of a command like @code{guix build}
  1116. should change from something like:
  1117. @example
  1118. $ guix build emacs --dry-run
  1119. The following derivations would be built:
  1120. /gnu/store/yr7bnx8xwcayd6j95r2clmkdl1qh688w-emacs-24.3.drv
  1121. /gnu/store/x8qsh1hlhgjx6cwsjyvybnfv2i37z23w-dbus-1.6.4.tar.gz.drv
  1122. /gnu/store/1ixwp12fl950d15h2cj11c73733jay0z-alsa-lib-
  1123. /gnu/store/nlma1pw0p603fpfiqy7kn4zm105r5dmw-util-linux-2.21.drv
  1124. @dots{}
  1125. @end example
  1126. @noindent
  1127. to something like:
  1128. @example
  1129. $ guix build emacs --dry-run
  1130. The following files would be downloaded:
  1131. /gnu/store/pk3n22lbq6ydamyymqkkz7i69wiwjiwi-emacs-24.3
  1132. /gnu/store/2ygn4ncnhrpr61rssa6z0d9x22si0va3-libjpeg-8d
  1133. /gnu/store/71yz6lgx4dazma9dwn2mcjxaah9w77jq-cairo-1.12.16
  1134. /gnu/store/7zdhgp0n1518lvfn8mb96sxqfmvqrl7v-libxrender-0.9.7
  1135. @dots{}
  1136. @end example
  1137. @noindent
  1138. This indicates that substitutes from @code{} are usable and
  1139. will be downloaded, when possible, for future builds.
  1140. Guix ignores substitutes that are not signed, or that are not signed by
  1141. one of the keys listed in the ACL. It also detects and raises an error
  1142. when attempting to use a substitute that has been tampered with.
  1143. The substitute mechanism can be disabled globally by running
  1144. @code{guix-daemon} with @code{--no-substitutes} (@pxref{Invoking
  1145. guix-daemon}). It can also be disabled temporarily by passing the
  1146. @code{--no-substitutes} option to @command{guix package}, @command{guix
  1147. build}, and other command-line tools.
  1148. Today, each individual's control over their own computing is at the
  1149. mercy of institutions, corporations, and groups with enough power and
  1150. determination to subvert the computing infrastructure and exploit its
  1151. weaknesses. While using @code{} substitutes can be
  1152. convenient, we encourage users to also build on their own, or even run
  1153. their own build farm, such that @code{} is less of an
  1154. interesting target. One way to help is by publishing the software you
  1155. build using @command{guix publish} so that others have one more choice
  1156. of server to download substitutes from (@pxref{Invoking guix publish}).
  1157. Guix has the foundations to maximize build reproducibility
  1158. (@pxref{Features}). In most cases, independent builds of a given
  1159. package or derivation should yield bit-identical results. Thus, through
  1160. a diverse set of independent package builds, we can strengthen the
  1161. integrity of our systems.
  1162. In the future, we want Guix to have support to publish and retrieve
  1163. binaries to/from other users, in a peer-to-peer fashion. If you would
  1164. like to discuss this project, join us on @email{}.
  1165. @node Packages with Multiple Outputs
  1166. @section Packages with Multiple Outputs
  1167. @cindex multiple-output packages
  1168. @cindex package outputs
  1169. Often, packages defined in Guix have a single @dfn{output}---i.e., the
  1170. source package leads exactly one directory in the store. When running
  1171. @command{guix package -i glibc}, one installs the default output of the
  1172. GNU libc package; the default output is called @code{out}, but its name
  1173. can be omitted as shown in this command. In this particular case, the
  1174. default output of @code{glibc} contains all the C header files, shared
  1175. libraries, static libraries, Info documentation, and other supporting
  1176. files.
  1177. Sometimes it is more appropriate to separate the various types of files
  1178. produced from a single source package into separate outputs. For
  1179. instance, the GLib C library (used by GTK+ and related packages)
  1180. installs more than 20 MiB of reference documentation as HTML pages.
  1181. To save space for users who do not need it, the documentation goes to a
  1182. separate output, called @code{doc}. To install the main GLib output,
  1183. which contains everything but the documentation, one would run:
  1184. @example
  1185. guix package -i glib
  1186. @end example
  1187. The command to install its documentation is:
  1188. @example
  1189. guix package -i glib:doc
  1190. @end example
  1191. Some packages install programs with different ``dependency footprints''.
  1192. For instance, the WordNet package install both command-line tools and
  1193. graphical user interfaces (GUIs). The former depend solely on the C
  1194. library, whereas the latter depend on Tcl/Tk and the underlying X
  1195. libraries. In this case, we leave the command-line tools in the default
  1196. output, whereas the GUIs are in a separate output. This allows users
  1197. who do not need the GUIs to save space.
  1198. There are several such multiple-output packages in the GNU distribution.
  1199. Other conventional output names include @code{lib} for libraries and
  1200. possibly header files, @code{bin} for stand-alone programs, and
  1201. @code{debug} for debugging information (@pxref{Installing Debugging
  1202. Files}). The outputs of a packages are listed in the third column of
  1203. the output of @command{guix package --list-available} (@pxref{Invoking
  1204. guix package}).
  1205. @node Invoking guix gc
  1206. @section Invoking @command{guix gc}
  1207. @cindex garbage collector
  1208. Packages that are installed but not used may be @dfn{garbage-collected}.
  1209. The @command{guix gc} command allows users to explicitly run the garbage
  1210. collector to reclaim space from the @file{/gnu/store} directory. It is
  1211. the @emph{only} way to remove files from @file{/gnu/store}---removing
  1212. files or directories manually may break it beyond repair!
  1213. The garbage collector has a set of known @dfn{roots}: any file under
  1214. @file{/gnu/store} reachable from a root is considered @dfn{live} and
  1215. cannot be deleted; any other file is considered @dfn{dead} and may be
  1216. deleted. The set of garbage collector roots includes default user
  1217. profiles, and may be augmented with @command{guix build --root}, for
  1218. example (@pxref{Invoking guix build}).
  1219. Prior to running @code{guix gc --collect-garbage} to make space, it is
  1220. often useful to remove old generations from user profiles; that way, old
  1221. package builds referenced by those generations can be reclaimed. This
  1222. is achieved by running @code{guix package --delete-generations}
  1223. (@pxref{Invoking guix package}).
  1224. The @command{guix gc} command has three modes of operation: it can be
  1225. used to garbage-collect any dead files (the default), to delete specific
  1226. files (the @code{--delete} option), to print garbage-collector
  1227. information, or for more advanced queries. The garbage collection
  1228. options are as follows:
  1229. @table @code
  1230. @item --collect-garbage[=@var{min}]
  1231. @itemx -C [@var{min}]
  1232. Collect garbage---i.e., unreachable @file{/gnu/store} files and
  1233. sub-directories. This is the default operation when no option is
  1234. specified.
  1235. When @var{min} is given, stop once @var{min} bytes have been collected.
  1236. @var{min} may be a number of bytes, or it may include a unit as a
  1237. suffix, such as @code{MiB} for mebibytes and @code{GB} for gigabytes
  1238. (@pxref{Block size, size specifications,, coreutils, GNU Coreutils}).
  1239. When @var{min} is omitted, collect all the garbage.
  1240. @item --delete
  1241. @itemx -d
  1242. Attempt to delete all the store files and directories specified as
  1243. arguments. This fails if some of the files are not in the store, or if
  1244. they are still live.
  1245. @item --list-dead
  1246. Show the list of dead files and directories still present in the
  1247. store---i.e., files and directories no longer reachable from any root.
  1248. @item --list-live
  1249. Show the list of live store files and directories.
  1250. @end table
  1251. In addition, the references among existing store files can be queried:
  1252. @table @code
  1253. @item --references
  1254. @itemx --referrers
  1255. List the references (respectively, the referrers) of store files given
  1256. as arguments.
  1257. @item --requisites
  1258. @itemx -R
  1259. List the requisites of the store files passed as arguments. Requisites
  1260. include the store files themselves, their references, and the references
  1261. of these, recursively. In other words, the returned list is the
  1262. @dfn{transitive closure} of the store files.
  1263. @end table
  1264. Lastly, the following options allow you to check the integrity of the
  1265. store and to control disk usage.
  1266. @table @option
  1267. @item --verify[=@var{options}]
  1268. @cindex integrity, of the store
  1269. @cindex integrity checking
  1270. Verify the integrity of the store.
  1271. By default, make sure that all the store items marked as valid in the
  1272. daemon's database actually exist in @file{/gnu/store}.
  1273. When provided, @var{options} must a comma-separated list containing one
  1274. or more of @code{contents} and @code{repair}.
  1275. When passing @option{--verify=contents}, the daemon will compute the
  1276. content hash of each store item and compare it against its hash in the
  1277. database. Hash mismatches are reported as data corruptions. Because it
  1278. traverses @emph{all the files in the store}, this command can take a
  1279. long time, especially on systems with a slow disk drive.
  1280. @cindex repairing the store
  1281. Using @option{--verify=repair} or @option{--verify=contents,repair}
  1282. causes the daemon to try to repair corrupt store items by fetching
  1283. substitutes for them (@pxref{Substitutes}). Because repairing is not
  1284. atomic, and thus potentially dangerous, it is available only to the
  1285. system administrator.
  1286. @item --optimize
  1287. @cindex deduplication
  1288. Optimize the store by hard-linking identical files---this is
  1289. @dfn{deduplication}.
  1290. The daemon performs deduplication after each successful build or archive
  1291. import, unless it was started with @code{--disable-deduplication}
  1292. (@pxref{Invoking guix-daemon, @code{--disable-deduplication}}). Thus,
  1293. this option is primarily useful when the daemon was running with
  1294. @code{--disable-deduplication}.
  1295. @end table
  1296. @node Invoking guix pull
  1297. @section Invoking @command{guix pull}
  1298. Packages are installed or upgraded to the latest version available in
  1299. the distribution currently available on your local machine. To update
  1300. that distribution, along with the Guix tools, you must run @command{guix
  1301. pull}: the command downloads the latest Guix source code and package
  1302. descriptions, and deploys it.
  1303. On completion, @command{guix package} will use packages and package
  1304. versions from this just-retrieved copy of Guix. Not only that, but all
  1305. the Guix commands and Scheme modules will also be taken from that latest
  1306. version. New @command{guix} sub-commands added by the update also
  1307. become available.
  1308. The @command{guix pull} command is usually invoked with no arguments,
  1309. but it supports the following options:
  1310. @table @code
  1311. @item --verbose
  1312. Produce verbose output, writing build logs to the standard error output.
  1313. @item --url=@var{url}
  1314. Download the source tarball of Guix from @var{url}.
  1315. By default, the tarball is taken from its canonical address at
  1316. @code{}, for the stable branch of Guix.
  1317. @item --bootstrap
  1318. Use the bootstrap Guile to build the latest Guix. This option is only
  1319. useful to Guix developers.
  1320. @end table
  1321. @node Invoking guix archive
  1322. @section Invoking @command{guix archive}
  1323. The @command{guix archive} command allows users to @dfn{export} files
  1324. from the store into a single archive, and to later @dfn{import} them.
  1325. In particular, it allows store files to be transferred from one machine
  1326. to another machine's store. For example, to transfer the @code{emacs}
  1327. package to a machine connected over SSH, one would run:
  1328. @example
  1329. guix archive --export -r emacs | ssh the-machine guix archive --import
  1330. @end example
  1331. @noindent
  1332. Similarly, a complete user profile may be transferred from one machine
  1333. to another like this:
  1334. @example
  1335. guix archive --export -r $(readlink -f ~/.guix-profile) | \
  1336. ssh the-machine guix-archive --import
  1337. @end example
  1338. @noindent
  1339. However, note that, in both examples, all of @code{emacs} and the
  1340. profile as well as all of their dependencies are transferred (due to
  1341. @code{-r}), regardless of what is already available in the target
  1342. machine's store. The @code{--missing} option can help figure out which
  1343. items are missing from the target's store.
  1344. Archives are stored in the ``Nix archive'' or ``Nar'' format, which is
  1345. comparable in spirit to `tar', but with a few noteworthy differences
  1346. that make it more appropriate for our purposes. First, rather than
  1347. recording all Unix meta-data for each file, the Nar format only mentions
  1348. the file type (regular, directory, or symbolic link); Unix permissions
  1349. and owner/group are dismissed. Second, the order in which directory
  1350. entries are stored always follows the order of file names according to
  1351. the C locale collation order. This makes archive production fully
  1352. deterministic.
  1353. When exporting, the daemon digitally signs the contents of the archive,
  1354. and that digital signature is appended. When importing, the daemon
  1355. verifies the signature and rejects the import in case of an invalid
  1356. signature or if the signing key is not authorized.
  1357. @c FIXME: Add xref to daemon doc about signatures.
  1358. The main options are:
  1359. @table @code
  1360. @item --export
  1361. Export the specified store files or packages (see below.) Write the
  1362. resulting archive to the standard output.
  1363. Dependencies are @emph{not} included in the output, unless
  1364. @code{--recursive} is passed.
  1365. @item -r
  1366. @itemx --recursive
  1367. When combined with @code{--export}, this instructs @command{guix
  1368. archive} to include dependencies of the given items in the archive.
  1369. Thus, the resulting archive is self-contained: it contains the closure
  1370. of the exported store items.
  1371. @item --import
  1372. Read an archive from the standard input, and import the files listed
  1373. therein into the store. Abort if the archive has an invalid digital
  1374. signature, or if it is signed by a public key not among the authorized
  1375. keys (see @code{--authorize} below.)
  1376. @item --missing
  1377. Read a list of store file names from the standard input, one per line,
  1378. and write on the standard output the subset of these files missing from
  1379. the store.
  1380. @item --generate-key[=@var{parameters}]
  1381. @cindex signing, archives
  1382. Generate a new key pair for the daemons. This is a prerequisite before
  1383. archives can be exported with @code{--export}. Note that this operation
  1384. usually takes time, because it needs to gather enough entropy to
  1385. generate the key pair.
  1386. The generated key pair is typically stored under @file{/etc/guix}, in
  1387. @file{} (public key) and @file{signing-key.sec} (private
  1388. key, which must be kept secret.) When @var{parameters} is omitted,
  1389. an ECDSA key using the Ed25519 curve is generated, or, for Libgcrypt
  1390. versions before 1.6.0, it is a 4096-bit RSA key.
  1391. Alternately, @var{parameters} can specify
  1392. @code{genkey} parameters suitable for Libgcrypt (@pxref{General
  1393. public-key related Functions, @code{gcry_pk_genkey},, gcrypt, The
  1394. Libgcrypt Reference Manual}).
  1395. @item --authorize
  1396. @cindex authorizing, archives
  1397. Authorize imports signed by the public key passed on standard input.
  1398. The public key must be in ``s-expression advanced format''---i.e., the
  1399. same format as the @file{} file.
  1400. The list of authorized keys is kept in the human-editable file
  1401. @file{/etc/guix/acl}. The file contains
  1402. @url{, ``advanced-format
  1403. s-expressions''} and is structured as an access-control list in the
  1404. @url{, Simple Public-Key Infrastructure
  1405. (SPKI)}.
  1406. @end table
  1407. To export store files as an archive to the standard output, run:
  1408. @example
  1409. guix archive --export @var{options} @var{specifications}...
  1410. @end example
  1411. @var{specifications} may be either store file names or package
  1412. specifications, as for @command{guix package} (@pxref{Invoking guix
  1413. package}). For instance, the following command creates an archive
  1414. containing the @code{gui} output of the @code{git} package and the main
  1415. output of @code{emacs}:
  1416. @example
  1417. guix archive --export git:gui /gnu/store/...-emacs-24.3 > great.nar
  1418. @end example
  1419. If the specified packages are not built yet, @command{guix archive}
  1420. automatically builds them. The build process may be controlled with the
  1421. same options that can be passed to the @command{guix build} command
  1422. (@pxref{Invoking guix build, common build options}).
  1423. @c *********************************************************************
  1424. @node Programming Interface
  1425. @chapter Programming Interface
  1426. GNU Guix provides several Scheme programming interfaces (APIs) to
  1427. define, build, and query packages. The first interface allows users to
  1428. write high-level package definitions. These definitions refer to
  1429. familiar packaging concepts, such as the name and version of a package,
  1430. its build system, and its dependencies. These definitions can then be
  1431. turned into concrete build actions.
  1432. Build actions are performed by the Guix daemon, on behalf of users. In a
  1433. standard setup, the daemon has write access to the store---the
  1434. @file{/gnu/store} directory---whereas users do not. The recommended
  1435. setup also has the daemon perform builds in chroots, under a specific
  1436. build users, to minimize interference with the rest of the system.
  1437. @cindex derivation
  1438. Lower-level APIs are available to interact with the daemon and the
  1439. store. To instruct the daemon to perform a build action, users actually
  1440. provide it with a @dfn{derivation}. A derivation is a low-level
  1441. representation of the build actions to be taken, and the environment in
  1442. which they should occur---derivations are to package definitions what
  1443. assembly is to C programs. The term ``derivation'' comes from the fact
  1444. that build results @emph{derive} from them.
  1445. This chapter describes all these APIs in turn, starting from high-level
  1446. package definitions.
  1447. @menu
  1448. * Defining Packages:: Defining new packages.
  1449. * Build Systems:: Specifying how packages are built.
  1450. * The Store:: Manipulating the package store.
  1451. * Derivations:: Low-level interface to package derivations.
  1452. * The Store Monad:: Purely functional interface to the store.
  1453. * G-Expressions:: Manipulating build expressions.
  1454. @end menu
  1455. @node Defining Packages
  1456. @section Defining Packages
  1457. The high-level interface to package definitions is implemented in the
  1458. @code{(guix packages)} and @code{(guix build-system)} modules. As an
  1459. example, the package definition, or @dfn{recipe}, for the GNU Hello
  1460. package looks like this:
  1461. @example
  1462. (define-module (gnu packages hello)
  1463. #:use-module (guix packages)
  1464. #:use-module (guix download)
  1465. #:use-module (guix build-system gnu)
  1466. #:use-module (guix licenses))
  1467. (define-public hello
  1468. (package
  1469. (name "hello")
  1470. (version "2.8")
  1471. (source (origin
  1472. (method url-fetch)
  1473. (uri (string-append "mirror://gnu/hello/hello-" version
  1474. ".tar.gz"))
  1475. (sha256
  1476. (base32 "0wqd8sjmxfskrflaxywc7gqw7sfawrfvdxd9skxawzfgyy0pzdz6"))))
  1477. (build-system gnu-build-system)
  1478. (arguments `(#:configure-flags '("--enable-silent-rules")))
  1479. (inputs `(("gawk" ,gawk)))
  1480. (synopsis "Hello, GNU world: An example GNU package")
  1481. (description "Guess what GNU Hello prints!")
  1482. (home-page "")
  1483. (license gpl3+)))
  1484. @end example
  1485. @noindent
  1486. Without being a Scheme expert, the reader may have guessed the meaning
  1487. of the various fields here. This expression binds variable @code{hello}
  1488. to a @code{<package>} object, which is essentially a record
  1489. (@pxref{SRFI-9, Scheme records,, guile, GNU Guile Reference Manual}).
  1490. This package object can be inspected using procedures found in the
  1491. @code{(guix packages)} module; for instance, @code{(package-name hello)}
  1492. returns---surprise!---@code{"hello"}.
  1493. With luck, you may be able to import part or all of the definition of
  1494. the package you are interested in from another repository, using the
  1495. @code{guix import} command (@pxref{Invoking guix import}).
  1496. In the example above, @var{hello} is defined into a module of its own,
  1497. @code{(gnu packages hello)}. Technically, this is not strictly
  1498. necessary, but it is convenient to do so: all the packages defined in
  1499. modules under @code{(gnu packages @dots{})} are automatically known to
  1500. the command-line tools (@pxref{Package Modules}).
  1501. There are a few points worth noting in the above package definition:
  1502. @itemize
  1503. @item
  1504. The @code{source} field of the package is an @code{<origin>} object
  1505. (@pxref{origin Reference}, for the complete reference).
  1506. Here, the @code{url-fetch} method from @code{(guix download)} is used,
  1507. meaning that the source is a file to be downloaded over FTP or HTTP.
  1508. The @code{mirror://gnu} prefix instructs @code{url-fetch} to use one of
  1509. the GNU mirrors defined in @code{(guix download)}.
  1510. The @code{sha256} field specifies the expected SHA256 hash of the file
  1511. being downloaded. It is mandatory, and allows Guix to check the
  1512. integrity of the file. The @code{(base32 @dots{})} form introduces the
  1513. base32 representation of the hash. You can obtain this information with
  1514. @code{guix download} (@pxref{Invoking guix download}) and @code{guix
  1515. hash} (@pxref{Invoking guix hash}).
  1516. @cindex patches
  1517. When needed, the @code{origin} form can also have a @code{patches} field
  1518. listing patches to be applied, and a @code{snippet} field giving a
  1519. Scheme expression to modify the source code.
  1520. @item
  1521. @cindex GNU Build System
  1522. The @code{build-system} field specifies the procedure to build the
  1523. package (@pxref{Build Systems}). Here, @var{gnu-build-system}
  1524. represents the familiar GNU Build System, where packages may be
  1525. configured, built, and installed with the usual @code{./configure &&
  1526. make && make check && make install} command sequence.
  1527. @item
  1528. The @code{arguments} field specifies options for the build system
  1529. (@pxref{Build Systems}). Here it is interpreted by
  1530. @var{gnu-build-system} as a request run @file{configure} with the
  1531. @code{--enable-silent-rules} flag.
  1532. @item
  1533. The @code{inputs} field specifies inputs to the build process---i.e.,
  1534. build-time or run-time dependencies of the package. Here, we define an
  1535. input called @code{"gawk"} whose value is that of the @var{gawk}
  1536. variable; @var{gawk} is itself bound to a @code{<package>} object.
  1537. Note that GCC, Coreutils, Bash, and other essential tools do not need to
  1538. be specified as inputs here. Instead, @var{gnu-build-system} takes care
  1539. of ensuring that they are present (@pxref{Build Systems}).
  1540. However, any other dependencies need to be specified in the
  1541. @code{inputs} field. Any dependency not specified here will simply be
  1542. unavailable to the build process, possibly leading to a build failure.
  1543. @end itemize
  1544. @xref{package Reference}, for a full description of possible fields.
  1545. Once a package definition is in place, the
  1546. package may actually be built using the @code{guix build} command-line
  1547. tool (@pxref{Invoking guix build}). @xref{Packaging Guidelines}, for
  1548. more information on how to test package definitions, and
  1549. @ref{Invoking guix lint}, for information on how to check a definition
  1550. for style conformance.
  1551. Eventually, updating the package definition to a new upstream version
  1552. can be partly automated by the @command{guix refresh} command
  1553. (@pxref{Invoking guix refresh}).
  1554. Behind the scenes, a derivation corresponding to the @code{<package>}
  1555. object is first computed by the @code{package-derivation} procedure.
  1556. That derivation is stored in a @code{.drv} file under @file{/gnu/store}.
  1557. The build actions it prescribes may then be realized by using the
  1558. @code{build-derivations} procedure (@pxref{The Store}).
  1559. @deffn {Scheme Procedure} package-derivation @var{store} @var{package} [@var{system}]
  1560. Return the @code{<derivation>} object of @var{package} for @var{system}
  1561. (@pxref{Derivations}).
  1562. @var{package} must be a valid @code{<package>} object, and @var{system}
  1563. must be a string denoting the target system type---e.g.,
  1564. @code{"x86_64-linux"} for an x86_64 Linux-based GNU system. @var{store}
  1565. must be a connection to the daemon, which operates on the store
  1566. (@pxref{The Store}).
  1567. @end deffn
  1568. @noindent
  1569. @cindex cross-compilation
  1570. Similarly, it is possible to compute a derivation that cross-builds a
  1571. package for some other system:
  1572. @deffn {Scheme Procedure} package-cross-derivation @var{store} @
  1573. @var{package} @var{target} [@var{system}]
  1574. Return the @code{<derivation>} object of @var{package} cross-built from
  1575. @var{system} to @var{target}.
  1576. @var{target} must be a valid GNU triplet denoting the target hardware
  1577. and operating system, such as @code{"mips64el-linux-gnu"}
  1578. (@pxref{Configuration Names, GNU configuration triplets,, configure, GNU
  1579. Configure and Build System}).
  1580. @end deffn
  1581. @menu
  1582. * package Reference :: The package data type.
  1583. * origin Reference:: The origin data type.
  1584. @end menu
  1585. @node package Reference
  1586. @subsection @code{package} Reference
  1587. This section summarizes all the options available in @code{package}
  1588. declarations (@pxref{Defining Packages}).
  1589. @deftp {Data Type} package
  1590. This is the data type representing a package recipe.
  1591. @table @asis
  1592. @item @code{name}
  1593. The name of the package, as a string.
  1594. @item @code{version}
  1595. The version of the package, as a string.
  1596. @item @code{source}
  1597. An origin object telling how the source code for the package should be
  1598. acquired (@pxref{origin Reference}).
  1599. @item @code{build-system}
  1600. The build system that should be used to build the package (@pxref{Build
  1601. Systems}).
  1602. @item @code{arguments} (default: @code{'()})
  1603. The arguments that should be passed to the build system. This is a
  1604. list, typically containing sequential keyword-value pairs.
  1605. @item @code{inputs} (default: @code{'()})
  1606. Package or derivation inputs to the build. This is a list of lists,
  1607. where each list has the name of the input (a string) as its first
  1608. element, a package or derivation object as its second element, and
  1609. optionally the name of the output of the package or derivation that
  1610. should be used, which defaults to @code{"out"}.
  1611. @item @anchor{package-propagated-inputs}@code{propagated-inputs} (default: @code{'()})
  1612. @cindex propagated inputs
  1613. This field is like @code{inputs}, but the specified packages will be
  1614. force-installed alongside the package they belong to
  1615. (@pxref{package-cmd-propagated-inputs, @command{guix package}}, for
  1616. information on how @command{guix package} deals with propagated inputs.)
  1617. For example this is necessary when a library needs headers of another
  1618. library to compile, or needs another shared library to be linked
  1619. alongside itself when a program wants to link to it.
  1620. @item @code{native-inputs} (default: @code{'()})
  1621. This field is like @code{inputs}, but in case of a cross-compilation it
  1622. will be ensured that packages for the architecture of the build machine
  1623. are present, such that executables from them can be used during the
  1624. build.
  1625. This is typically where you would list tools needed at build time but
  1626. not at run time, such as Autoconf, Automake, pkg-config, Gettext, or
  1627. Bison. @command{guix lint} can report likely mistakes in this area
  1628. (@pxref{Invoking guix lint}).
  1629. @item @code{self-native-input?} (default: @code{#f})
  1630. This is a Boolean field telling whether the package should use itself as
  1631. a native input when cross-compiling.
  1632. @item @code{outputs} (default: @code{'("out")})
  1633. The list of output names of the package. @xref{Packages with Multiple
  1634. Outputs}, for typical uses of additional outputs.
  1635. @item @code{native-search-paths} (default: @code{'()})
  1636. @itemx @code{search-paths} (default: @code{'()})
  1637. A list of @code{search-path-specification} objects describing
  1638. search-path environment variables honored by the package.
  1639. @item @code{replacement} (default: @code{#f})
  1640. This must either @code{#f} or a package object that will be used as a
  1641. @dfn{replacement} for this package. @xref{Security Updates, grafts},
  1642. for details.
  1643. @item @code{synopsis}
  1644. A one-line description of the package.
  1645. @item @code{description}
  1646. A more elaborate description of the package.
  1647. @item @code{license}
  1648. The license of the package; a value from @code{(guix licenses)}.
  1649. @item @code{home-page}
  1650. The URL to the home-page of the package, as a string.
  1651. @item @code{supported-systems} (default: @var{%supported-systems})
  1652. The list of systems supported by the package, as strings of the form
  1653. @code{architecture-kernel}, for example @code{"x86_64-linux"}.
  1654. @item @code{maintainers} (default: @code{'()})
  1655. The list of maintainers of the package, as @code{maintainer} objects.
  1656. @item @code{location} (default: source location of the @code{package} form)
  1657. The source location of the package. It's useful to override this when
  1658. inheriting from another package, in which case this field is not
  1659. automatically corrected.
  1660. @end table
  1661. @end deftp
  1662. @node origin Reference
  1663. @subsection @code{origin} Reference
  1664. This section summarizes all the options available in @code{origin}
  1665. declarations (@pxref{Defining Packages}).
  1666. @deftp {Data Type} origin
  1667. This is the data type representing a source code origin.
  1668. @table @asis
  1669. @item @code{uri}
  1670. An object containing the URI of the source. The object type depends on
  1671. the @code{method} (see below). For example, when using the
  1672. @var{url-fetch} method of @code{(guix download)}, the valid @code{uri}
  1673. values are: a URL represented as a string, or a list thereof.
  1674. @item @code{method}
  1675. A procedure that will handle the URI.
  1676. Examples include:
  1677. @table @asis
  1678. @item @var{url-fetch} from @code{(guix download)}
  1679. download a file the HTTP, HTTPS, or FTP URL specified in the
  1680. @code{uri} field;
  1681. @item @var{git-fetch} from @code{(guix git-download)}
  1682. clone the Git version control repository, and check out the revision
  1683. specified in the @code{uri} field as a @code{git-reference} object; a
  1684. @code{git-reference} looks like this:
  1685. @example
  1686. (git-reference
  1687. (url "git://")
  1688. (commit "v4.1.5.1"))
  1689. @end example
  1690. @end table
  1691. @item @code{sha256}
  1692. A bytevector containing the SHA-256 hash of the source. Typically the
  1693. @code{base32} form is used here to generate the bytevector from a
  1694. base-32 string.
  1695. @item @code{file-name} (default: @code{#f})
  1696. The file name under which the source code should be saved. When this is
  1697. @code{#f}, a sensible default value will be used in most cases. In case
  1698. the source is fetched from a URL, the file name from the URL will be
  1699. used. For version control checkouts, it's recommended to provide the
  1700. file name explicitly because the default is not very descriptive.
  1701. @item @code{patches} (default: @code{'()})
  1702. A list of file names containing patches to be applied to the source.
  1703. @item @code{snippet} (default: @code{#f})
  1704. A quoted piece of code that will be run in the source directory to make
  1705. any modifications, which is sometimes more convenient than a patch.
  1706. @item @code{patch-flags} (default: @code{'("-p1")})
  1707. A list of command-line flags that should be passed to the @code{patch}
  1708. command.
  1709. @item @code{patch-inputs} (default: @code{#f})
  1710. Input packages or derivations to the patching process. When this is
  1711. @code{#f}, the usual set of inputs necessary for patching are provided,
  1712. such as GNU@tie{}Patch.
  1713. @item @code{modules} (default: @code{'()})
  1714. A list of Guile modules that should be loaded during the patching
  1715. process and while running the code in the @code{snippet} field.
  1716. @item @code{imported-modules} (default: @code{'()})
  1717. The list of Guile modules to import in the patch derivation, for use by
  1718. the @code{snippet}.
  1719. @item @code{patch-guile} (default: @code{#f})
  1720. The Guile package that should be used in the patching process. When
  1721. this is @code{#f}, a sensible default is used.
  1722. @end table
  1723. @end deftp
  1724. @node Build Systems
  1725. @section Build Systems
  1726. @cindex build system
  1727. Each package definition specifies a @dfn{build system} and arguments for
  1728. that build system (@pxref{Defining Packages}). This @code{build-system}
  1729. field represents the build procedure of the package, as well implicit
  1730. dependencies of that build procedure.
  1731. Build systems are @code{<build-system>} objects. The interface to
  1732. create and manipulate them is provided by the @code{(guix build-system)}
  1733. module, and actual build systems are exported by specific modules.
  1734. @cindex bag (low-level package representation)
  1735. Under the hood, build systems first compile package objects to
  1736. @dfn{bags}. A @dfn{bag} is like a package, but with less
  1737. ornamentation---in other words, a bag is a lower-level representation of
  1738. a package, which includes all the inputs of that package, including some
  1739. that were implicitly added by the build system. This intermediate
  1740. representation is then compiled to a derivation (@pxref{Derivations}).
  1741. Build systems accept an optional list of @dfn{arguments}. In package
  1742. definitions, these are passed @i{via} the @code{arguments} field
  1743. (@pxref{Defining Packages}). They are typically keyword arguments
  1744. (@pxref{Optional Arguments, keyword arguments in Guile,, guile, GNU
  1745. Guile Reference Manual}). The value of these arguments is usually
  1746. evaluated in the @dfn{build stratum}---i.e., by a Guile process launched
  1747. by the daemon (@pxref{Derivations}).
  1748. The main build system is @var{gnu-build-system}, which implements the
  1749. standard build procedure for GNU packages and many other packages. It
  1750. is provided by the @code{(guix build-system gnu)} module.
  1751. @defvr {Scheme Variable} gnu-build-system
  1752. @var{gnu-build-system} represents the GNU Build System, and variants
  1753. thereof (@pxref{Configuration, configuration and makefile conventions,,
  1754. standards, GNU Coding Standards}).
  1755. @cindex build phases
  1756. In a nutshell, packages using it configured, built, and installed with
  1757. the usual @code{./configure && make && make check && make install}
  1758. command sequence. In practice, a few additional steps are often needed.
  1759. All these steps are split up in separate @dfn{phases},
  1760. notably@footnote{Please see the @code{(guix build gnu-build-system)}
  1761. modules for more details about the build phases.}:
  1762. @table @code
  1763. @item unpack
  1764. Unpack the source tarball, and change the current directory to the
  1765. extracted source tree. If the source is actually a directory, copy it
  1766. to the build tree, and enter that directory.
  1767. @item patch-source-shebangs
  1768. Patch shebangs encountered in source files so they refer to the right
  1769. store file names. For instance, this changes @code{#!/bin/sh} to
  1770. @code{#!/gnu/store/@dots{}-bash-4.3/bin/sh}.
  1771. @item configure
  1772. Run the @file{configure} script with a number of default options, such
  1773. as @code{--prefix=/gnu/store/@dots{}}, as well as the options specified
  1774. by the @code{#:configure-flags} argument.
  1775. @item build
  1776. Run @code{make} with the list of flags specified with
  1777. @code{#:make-flags}. If the @code{#:parallel-builds?} argument is true
  1778. (the default), build with @code{make -j}.
  1779. @item check
  1780. Run @code{make check}, or some other target specified with
  1781. @code{#:test-target}, unless @code{#:tests? #f} is passed. If the
  1782. @code{#:parallel-tests?} argument is true (the default), run @code{make
  1783. check -j}.
  1784. @item install
  1785. Run @code{make install} with the flags listed in @code{#:make-flags}.
  1786. @item patch-shebangs
  1787. Patch shebangs on the installed executable files.
  1788. @item strip
  1789. Strip debugging symbols from ELF files (unless @code{#:strip-binaries?}
  1790. is false), copying them to the @code{debug} output when available
  1791. (@pxref{Installing Debugging Files}).
  1792. @end table
  1793. @vindex %standard-phases
  1794. The build-side module @code{(guix build gnu-build-system)} defines
  1795. @var{%standard-phases} as the default list of build phases.
  1796. @var{%standard-phases} is a list of symbol/procedure pairs, where the
  1797. procedure implements the actual phase.
  1798. The list of phases used for a particular package can be changed with the
  1799. @code{#:phases} parameter. For instance, passing:
  1800. @example
  1801. #:phases (alist-delete 'configure %standard-phases)
  1802. @end example
  1803. means that all the phases described above will be used, except the
  1804. @code{configure} phase.
  1805. In addition, this build system ensures that the ``standard'' environment
  1806. for GNU packages is available. This includes tools such as GCC, libc,
  1807. Coreutils, Bash, Make, Diffutils, grep, and sed (see the @code{(guix
  1808. build-system gnu)} module for a complete list.) We call these the
  1809. @dfn{implicit inputs} of a package, because package definitions don't
  1810. have to mention them.
  1811. @end defvr
  1812. Other @code{<build-system>} objects are defined to support other
  1813. conventions and tools used by free software packages. They inherit most
  1814. of @var{gnu-build-system}, and differ mainly in the set of inputs
  1815. implicitly added to the build process, and in the list of phases
  1816. executed. Some of these build systems are listed below.
  1817. @defvr {Scheme Variable} cmake-build-system
  1818. This variable is exported by @code{(guix build-system cmake)}. It
  1819. implements the build procedure for packages using the
  1820. @url{, CMake build tool}.
  1821. It automatically adds the @code{cmake} package to the set of inputs.
  1822. Which package is used can be specified with the @code{#:cmake}
  1823. parameter.
  1824. The @code{#:configure-flags} parameter is taken as a list of flags
  1825. passed to the @command{cmake} command. The @code{#:build-type}
  1826. parameter specifies in abstract terms the flags passed to the compiler;
  1827. it defaults to @code{"RelWithDebInfo"} (short for ``release mode with
  1828. debugging information''), which roughly means that code is compiled with
  1829. @code{-O2 -g}, as is the case for Autoconf-based packages by default.
  1830. @end defvr
  1831. @defvr {Scheme Variable} glib-or-gtk-build-system
  1832. This variable is exported by @code{(guix build-system glib-or-gtk)}. It
  1833. is intended for use with packages making use of GLib or GTK+.
  1834. This build system adds the following two phases to the ones defined by
  1835. @var{gnu-build-system}:
  1836. @table @code
  1837. @item glib-or-gtk-wrap
  1838. The phase @code{glib-or-gtk-wrap} ensures that programs found under
  1839. @file{bin/} are able to find GLib's ``schemas'' and
  1840. @uref{, GTK+
  1841. modules}. This is achieved by wrapping the programs in launch scripts
  1842. that appropriately set the @code{XDG_DATA_DIRS} and @code{GTK_PATH}
  1843. environment variables.
  1844. It is possible to exclude specific package outputs from that wrapping
  1845. process by listing their names in the
  1846. @code{#:glib-or-gtk-wrap-excluded-outputs} parameter. This is useful
  1847. when an output is known not to contain any GLib or GTK+ binaries, and
  1848. where wrapping would gratuitously add a dependency of that output on
  1849. GLib and GTK+.
  1850. @item glib-or-gtk-compile-schemas
  1851. The phase @code{glib-or-gtk-compile-schemas} makes sure that all GLib's
  1852. @uref{,
  1853. GSettings schemas} are compiled. Compilation is performed by the
  1854. @command{glib-compile-schemas} program. It is provided by the package
  1855. @code{glib:bin} which is automatically imported by the build system.
  1856. The @code{glib} package providing @command{glib-compile-schemas} can be
  1857. specified with the @code{#:glib} parameter.
  1858. @end table
  1859. Both phases are executed after the @code{install} phase.
  1860. @end defvr
  1861. @defvr {Scheme Variable} python-build-system
  1862. This variable is exported by @code{(guix build-system python)}. It
  1863. implements the more or less standard build procedure used by Python
  1864. packages, which consists in running @code{python build} and
  1865. then @code{python install --prefix=/gnu/store/@dots{}}.
  1866. For packages that install stand-alone Python programs under @code{bin/},
  1867. it takes care of wrapping these programs so their @code{PYTHONPATH}
  1868. environment variable points to all the Python libraries they depend on.
  1869. Which Python package is used can be specified with the @code{#:python}
  1870. parameter.
  1871. @end defvr
  1872. @defvr {Scheme Variable} perl-build-system
  1873. This variable is exported by @code{(guix build-system perl)}. It
  1874. implements the standard build procedure for Perl packages, which either
  1875. consists in running @code{perl Build.PL --prefix=/gnu/store/@dots{}},
  1876. followed by @code{Build} and @code{Build install}; or in running
  1877. @code{perl Makefile.PL PREFIX=/gnu/store/@dots{}}, followed by
  1878. @code{make} and @code{make install}; depending on which of
  1879. @code{Build.PL} or @code{Makefile.PL} is present in the package
  1880. distribution. Preference is given to the former if both @code{Build.PL}
  1881. and @code{Makefile.PL} exist in the package distribution. This
  1882. preference can be reversed by specifying @code{#t} for the
  1883. @code{#:make-maker?} parameter.
  1884. The initial @code{perl Makefile.PL} or @code{perl Build.PL} invocation
  1885. passes flags specified by the @code{#:make-maker-flags} or
  1886. @code{#:module-build-flags} parameter, respectively.
  1887. Which Perl package is used can be specified with @code{#:perl}.
  1888. @end defvr
  1889. @defvr {Scheme Variable} ruby-build-system
  1890. This variable is exported by @code{(guix build-system ruby)}. It
  1891. implements the RubyGems build procedure used by Ruby packages, which
  1892. involves running @code{gem build} followed by @code{gem install}.
  1893. Which Ruby package is used can be specified with the @code{#:ruby}
  1894. parameter.
  1895. @end defvr
  1896. @defvr {Scheme Variable} waf-build-system
  1897. This variable is exported by @code{(guix build-system waf)}. It
  1898. implements a build procedure around the @code{waf} script. The common
  1899. phases---@code{configure}, @code{build}, and @code{install}---are
  1900. implemented by passing their names as arguments to the @code{waf}
  1901. script.
  1902. The @code{waf} script is executed by the Python interpreter. Which
  1903. Python package is used to run the script can be specified with the
  1904. @code{#:python} parameter.
  1905. @end defvr
  1906. @defvr {Scheme Variable} haskell-build-system
  1907. This variable is exported by @code{(guix build-system haskell)}. It
  1908. implements the Cabal build procedure used by Haskell packages, which
  1909. involves running @code{runhaskell Setup.hs configure
  1910. --prefix=/gnu/store/@dots{}} and @code{runhaskell Setup.hs build}.
  1911. Instead of installing the package by running @code{runhaskell Setup.hs
  1912. install}, to avoid trying to register libraries in the read-only
  1913. compiler store directory, the build system uses @code{runhaskell
  1914. Setup.hs copy}, followed by @code{runhaskell Setup.hs register}. In
  1915. addition, the build system generates the package documentation by
  1916. running @code{runhaskell Setup.hs haddock}, unless @code{#:haddock? #f}
  1917. is passed. Optional Haddock parameters can be passed with the help of
  1918. the @code{#:haddock-flags} parameter. If the file @code{Setup.hs} is
  1919. not found, the build system looks for @code{Setup.lhs} instead.
  1920. Which Haskell compiler is used can be specified with the @code{#:haskell}
  1921. parameter which defaults to @code{ghc}.
  1922. @end defvr
  1923. Lastly, for packages that do not need anything as sophisticated, a
  1924. ``trivial'' build system is provided. It is trivial in the sense that
  1925. it provides basically no support: it does not pull any implicit inputs,
  1926. and does not have a notion of build phases.
  1927. @defvr {Scheme Variable} trivial-build-system
  1928. This variable is exported by @code{(guix build-system trivial)}.
  1929. This build system requires a @code{#:builder} argument. This argument
  1930. must be a Scheme expression that builds the package's output(s)---as
  1931. with @code{build-expression->derivation} (@pxref{Derivations,
  1932. @code{build-expression->derivation}}).
  1933. @end defvr
  1934. @node The Store
  1935. @section The Store
  1936. @cindex store
  1937. @cindex store paths
  1938. Conceptually, the @dfn{store} is where derivations that have been
  1939. successfully built are stored---by default, under @file{/gnu/store}.
  1940. Sub-directories in the store are referred to as @dfn{store paths}. The
  1941. store has an associated database that contains information such has the
  1942. store paths referred to by each store path, and the list of @emph{valid}
  1943. store paths---paths that result from a successful build.
  1944. The store is always accessed by the daemon on behalf of its clients
  1945. (@pxref{Invoking guix-daemon}). To manipulate the store, clients
  1946. connect to the daemon over a Unix-domain socket, send it requests, and
  1947. read the result---these are remote procedure calls, or RPCs.
  1948. The @code{(guix store)} module provides procedures to connect to the
  1949. daemon, and to perform RPCs. These are described below.
  1950. @deffn {Scheme Procedure} open-connection [@var{file}] [#:reserve-space? #t]
  1951. Connect to the daemon over the Unix-domain socket at @var{file}. When
  1952. @var{reserve-space?} is true, instruct it to reserve a little bit of
  1953. extra space on the file system so that the garbage collector can still
  1954. operate, should the disk become full. Return a server object.
  1955. @var{file} defaults to @var{%default-socket-path}, which is the normal
  1956. location given the options that were passed to @command{configure}.
  1957. @end deffn
  1958. @deffn {Scheme Procedure} close-connection @var{server}
  1959. Close the connection to @var{server}.
  1960. @end deffn
  1961. @defvr {Scheme Variable} current-build-output-port
  1962. This variable is bound to a SRFI-39 parameter, which refers to the port
  1963. where build and error logs sent by the daemon should be written.
  1964. @end defvr
  1965. Procedures that make RPCs all take a server object as their first
  1966. argument.
  1967. @deffn {Scheme Procedure} valid-path? @var{server} @var{path}
  1968. Return @code{#t} when @var{path} is a valid store path.
  1969. @end deffn
  1970. @deffn {Scheme Procedure} add-text-to-store @var{server} @var{name} @var{text} [@var{references}]
  1971. Add @var{text} under file @var{name} in the store, and return its store
  1972. path. @var{references} is the list of store paths referred to by the
  1973. resulting store path.
  1974. @end deffn
  1975. @deffn {Scheme Procedure} build-derivations @var{server} @var{derivations}
  1976. Build @var{derivations} (a list of @code{<derivation>} objects or
  1977. derivation paths), and return when the worker is done building them.
  1978. Return @code{#t} on success.
  1979. @end deffn
  1980. Note that the @code{(guix monads)} module provides a monad as well as
  1981. monadic versions of the above procedures, with the goal of making it
  1982. more convenient to work with code that accesses the store (@pxref{The
  1983. Store Monad}).
  1984. @c FIXME
  1985. @i{This section is currently incomplete.}
  1986. @node Derivations
  1987. @section Derivations
  1988. @cindex derivations
  1989. Low-level build actions and the environment in which they are performed
  1990. are represented by @dfn{derivations}. A derivation contain the
  1991. following pieces of information:
  1992. @itemize
  1993. @item
  1994. The outputs of the derivation---derivations produce at least one file or
  1995. directory in the store, but may produce more.
  1996. @item
  1997. The inputs of the derivations, which may be other derivations or plain
  1998. files in the store (patches, build scripts, etc.)
  1999. @item
  2000. The system type targeted by the derivation---e.g., @code{x86_64-linux}.
  2001. @item
  2002. The file name of a build script in the store, along with the arguments
  2003. to be passed.
  2004. @item
  2005. A list of environment variables to be defined.
  2006. @end itemize
  2007. @cindex derivation path
  2008. Derivations allow clients of the daemon to communicate build actions to
  2009. the store. They exist in two forms: as an in-memory representation,
  2010. both on the client- and daemon-side, and as files in the store whose
  2011. name end in @code{.drv}---these files are referred to as @dfn{derivation
  2012. paths}. Derivations paths can be passed to the @code{build-derivations}
  2013. procedure to perform the build actions they prescribe (@pxref{The
  2014. Store}).
  2015. The @code{(guix derivations)} module provides a representation of
  2016. derivations as Scheme objects, along with procedures to create and
  2017. otherwise manipulate derivations. The lowest-level primitive to create
  2018. a derivation is the @code{derivation} procedure:
  2019. @deffn {Scheme Procedure} derivation @var{store} @var{name} @var{builder} @
  2020. @var{args} [#:outputs '("out")] [#:hash #f] [#:hash-algo #f] @
  2021. [#:recursive? #f] [#:inputs '()] [#:env-vars '()] @
  2022. [#:system (%current-system)] [#:references-graphs #f] @
  2023. [#:allowed-references #f] [#:leaked-env-vars #f] [#:local-build? #f]
  2024. Build a derivation with the given arguments, and return the resulting
  2025. @code{<derivation>} object.
  2026. When @var{hash} and @var{hash-algo} are given, a
  2027. @dfn{fixed-output derivation} is created---i.e., one whose result is
  2028. known in advance, such as a file download. If, in addition,
  2029. @var{recursive?} is true, then that fixed output may be an executable
  2030. file or a directory and @var{hash} must be the hash of an archive
  2031. containing this output.
  2032. When @var{references-graphs} is true, it must be a list of file
  2033. name/store path pairs. In that case, the reference graph of each store
  2034. path is exported in the build environment in the corresponding file, in
  2035. a simple text format.
  2036. When @var{allowed-references} is true, it must be a list of store items
  2037. or outputs that the derivation's output may refer to.
  2038. When @var{leaked-env-vars} is true, it must be a list of strings
  2039. denoting environment variables that are allowed to ``leak'' from the
  2040. daemon's environment to the build environment. This is only applicable
  2041. to fixed-output derivations---i.e., when @var{hash} is true. The main
  2042. use is to allow variables such as @code{http_proxy} to be passed to
  2043. derivations that download files.
  2044. When @var{local-build?} is true, declare that the derivation is not a
  2045. good candidate for offloading and should rather be built locally
  2046. (@pxref{Daemon Offload Setup}). This is the case for small derivations
  2047. where the costs of data transfers would outweigh the benefits.
  2048. @end deffn
  2049. @noindent
  2050. Here's an example with a shell script as its builder, assuming
  2051. @var{store} is an open connection to the daemon, and @var{bash} points
  2052. to a Bash executable in the store:
  2053. @lisp
  2054. (use-modules (guix utils)
  2055. (guix store)
  2056. (guix derivations))
  2057. (let ((builder ; add the Bash script to the store
  2058. (add-text-to-store store ""
  2059. "echo hello world > $out\n" '())))
  2060. (derivation store "foo"
  2061. bash `("-e" ,builder)
  2062. #:inputs `((,bash) (,builder))
  2063. #:env-vars '(("HOME" . "/homeless"))))
  2064. @result{} #<derivation /gnu/store/@dots{}-foo.drv => /gnu/store/@dots{}-foo>
  2065. @end lisp
  2066. As can be guessed, this primitive is cumbersome to use directly. A
  2067. better approach is to write build scripts in Scheme, of course! The
  2068. best course of action for that is to write the build code as a
  2069. ``G-expression'', and to pass it to @code{gexp->derivation}. For more
  2070. information, @pxref{G-Expressions}.
  2071. Once upon a time, @code{gexp->derivation} did not exist and constructing
  2072. derivations with build code written in Scheme was achieved with
  2073. @code{build-expression->derivation}, documented below. This procedure
  2074. is now deprecated in favor of the much nicer @code{gexp->derivation}.
  2075. @deffn {Scheme Procedure} build-expression->derivation @var{store} @
  2076. @var{name} @var{exp} @
  2077. [#:system (%current-system)] [#:inputs '()] @
  2078. [#:outputs '("out")] [#:hash #f] [#:hash-algo #f] @
  2079. [#:recursive? #f] [#:env-vars '()] [#:modules '()] @
  2080. [#:references-graphs #f] [#:allowed-references #f] @
  2081. [#:local-build? #f] [#:guile-for-build #f]
  2082. Return a derivation that executes Scheme expression @var{exp} as a
  2083. builder for derivation @var{name}. @var{inputs} must be a list of
  2084. @code{(name drv-path sub-drv)} tuples; when @var{sub-drv} is omitted,
  2085. @code{"out"} is assumed. @var{modules} is a list of names of Guile
  2086. modules from the current search path to be copied in the store,
  2087. compiled, and made available in the load path during the execution of
  2088. @var{exp}---e.g., @code{((guix build utils) (guix build
  2089. gnu-build-system))}.
  2090. @var{exp} is evaluated in an environment where @code{%outputs} is bound
  2091. to a list of output/path pairs, and where @code{%build-inputs} is bound
  2092. to a list of string/output-path pairs made from @var{inputs}.
  2093. Optionally, @var{env-vars} is a list of string pairs specifying the name
  2094. and value of environment variables visible to the builder. The builder
  2095. terminates by passing the result of @var{exp} to @code{exit}; thus, when
  2096. @var{exp} returns @code{#f}, the build is considered to have failed.
  2097. @var{exp} is built using @var{guile-for-build} (a derivation). When
  2098. @var{guile-for-build} is omitted or is @code{#f}, the value of the
  2099. @code{%guile-for-build} fluid is used instead.
  2100. See the @code{derivation} procedure for the meaning of
  2101. @var{references-graphs}, @var{allowed-references}, and @var{local-build?}.
  2102. @end deffn
  2103. @noindent
  2104. Here's an example of a single-output derivation that creates a directory
  2105. containing one file:
  2106. @lisp
  2107. (let ((builder '(let ((out (assoc-ref %outputs "out")))
  2108. (mkdir out) ; create /gnu/store/@dots{}-goo
  2109. (call-with-output-file (string-append out "/test")
  2110. (lambda (p)
  2111. (display '(hello guix) p))))))
  2112. (build-expression->derivation store "goo" builder))
  2113. @result{} #<derivation /gnu/store/@dots{}-goo.drv => @dots{}>
  2114. @end lisp
  2115. @node The Store Monad
  2116. @section The Store Monad
  2117. @cindex monad
  2118. The procedures that operate on the store described in the previous
  2119. sections all take an open connection to the build daemon as their first
  2120. argument. Although the underlying model is functional, they either have
  2121. side effects or depend on the current state of the store.
  2122. The former is inconvenient: the connection to the build daemon has to be
  2123. carried around in all those functions, making it impossible to compose
  2124. functions that do not take that parameter with functions that do. The
  2125. latter can be problematic: since store operations have side effects
  2126. and/or depend on external state, they have to be properly sequenced.
  2127. @cindex monadic values
  2128. @cindex monadic functions
  2129. This is where the @code{(guix monads)} module comes in. This module
  2130. provides a framework for working with @dfn{monads}, and a particularly
  2131. useful monad for our uses, the @dfn{store monad}. Monads are a
  2132. construct that allows two things: associating ``context'' with values
  2133. (in our case, the context is the store), and building sequences of
  2134. computations (here computations include accesses to the store.) Values
  2135. in a monad---values that carry this additional context---are called
  2136. @dfn{monadic values}; procedures that return such values are called
  2137. @dfn{monadic procedures}.
  2138. Consider this ``normal'' procedure:
  2139. @example
  2140. (define (sh-symlink store)
  2141. ;; Return a derivation that symlinks the 'bash' executable.
  2142. (let* ((drv (package-derivation store bash))
  2143. (out (derivation->output-path drv))
  2144. (sh (string-append out "/bin/bash")))
  2145. (build-expression->derivation store "sh"
  2146. `(symlink ,sh %output))))
  2147. @end example
  2148. Using @code{(guix monads)} and @code{(guix gexp)}, it may be rewritten
  2149. as a monadic function:
  2150. @example
  2151. (define (sh-symlink)
  2152. ;; Same, but return a monadic value.
  2153. (mlet %store-monad ((drv (package->derivation bash)))
  2154. (gexp->derivation "sh"
  2155. #~(symlink (string-append #$drv "/bin/bash")
  2156. #$output))))
  2157. @end example
  2158. There several things to note in the second version: the @code{store}
  2159. parameter is now implicit and is ``threaded'' in the calls to the
  2160. @code{package->derivation} and @code{gexp->derivation} monadic
  2161. procedures, and the monadic value returned by @code{package->derivation}
  2162. is @dfn{bound} using @code{mlet} instead of plain @code{let}.
  2163. As it turns out, the call to @code{package->derivation} can even be
  2164. omitted since it will take place implicitly, as we will see later
  2165. (@pxref{G-Expressions}):
  2166. @example
  2167. (define (sh-symlink)
  2168. (gexp->derivation "sh"
  2169. #~(symlink (string-append #$bash "/bin/bash")
  2170. #$output)))
  2171. @end example
  2172. Calling the monadic @code{sh-symlink} has no effect. To get the desired
  2173. effect, one must use @code{run-with-store}:
  2174. @example
  2175. (run-with-store (open-connection) (sh-symlink))
  2176. @result{} /gnu/store/...-sh-symlink
  2177. @end example
  2178. Note that the @code{(guix monad-repl)} module extends Guile's REPL with
  2179. new ``meta-commands'' to make it easier to deal with monadic procedures:
  2180. @code{run-in-store}, and @code{enter-store-monad}. The former, is used
  2181. to ``run'' a single monadic value through the store:
  2182. @example
  2183. scheme@@(guile-user)> ,run-in-store (package->derivation hello)
  2184. $1 = #<derivation /gnu/store/@dots{}-hello-2.9.drv => @dots{}>
  2185. @end example
  2186. The latter enters a recursive REPL, where all the return values are
  2187. automatically run through the store:
  2188. @example
  2189. scheme@@(guile-user)> ,enter-store-monad
  2190. store-monad@@(guile-user) [1]> (package->derivation hello)
  2191. $2 = #<derivation /gnu/store/@dots{}-hello-2.9.drv => @dots{}>
  2192. store-monad@@(guile-user) [1]> (text-file "foo" "Hello!")
  2193. $3 = "/gnu/store/@dots{}-foo"
  2194. store-monad@@(guile-user) [1]> ,q
  2195. scheme@@(guile-user)>
  2196. @end example
  2197. @noindent
  2198. Note that non-monadic values cannot be returned in the
  2199. @code{store-monad} REPL.
  2200. The main syntactic forms to deal with monads in general are provided by
  2201. the @code{(guix monads)} module and are described below.
  2202. @deffn {Scheme Syntax} with-monad @var{monad} @var{body} ...
  2203. Evaluate any @code{>>=} or @code{return} forms in @var{body} as being
  2204. in @var{monad}.
  2205. @end deffn
  2206. @deffn {Scheme Syntax} return @var{val}
  2207. Return a monadic value that encapsulates @var{val}.
  2208. @end deffn
  2209. @deffn {Scheme Syntax} >>= @var{mval} @var{mproc} ...
  2210. @dfn{Bind} monadic value @var{mval}, passing its ``contents'' to monadic
  2211. procedures @var{mproc}@dots{}@footnote{This operation is commonly
  2212. referred to as ``bind'', but that name denotes an unrelated procedure in
  2213. Guile. Thus we use this somewhat cryptic symbol inherited from the
  2214. Haskell language.}. There can be one @var{mproc} or several of them, as
  2215. in this example:
  2216. @example
  2217. (run-with-state
  2218. (with-monad %state-monad
  2219. (>>= (return 1)
  2220. (lambda (x) (return (+ 1 x)))
  2221. (lambda (x) (return (* 2 x)))))
  2222. 'some-state)
  2223. @result{} 4
  2224. @result{} some-state
  2225. @end example
  2226. @end deffn
  2227. @deffn {Scheme Syntax} mlet @var{monad} ((@var{var} @var{mval}) ...) @
  2228. @var{body} ...
  2229. @deffnx {Scheme Syntax} mlet* @var{monad} ((@var{var} @var{mval}) ...) @
  2230. @var{body} ...
  2231. Bind the variables @var{var} to the monadic values @var{mval} in
  2232. @var{body}. The form (@var{var} -> @var{val}) binds @var{var} to the
  2233. ``normal'' value @var{val}, as per @code{let}.
  2234. @code{mlet*} is to @code{mlet} what @code{let*} is to @code{let}
  2235. (@pxref{Local Bindings,,, guile, GNU Guile Reference Manual}).
  2236. @end deffn
  2237. @deffn {Scheme System} mbegin @var{monad} @var{mexp} ...
  2238. Bind @var{mexp} and the following monadic expressions in sequence,
  2239. returning the result of the last expression.
  2240. This is akin to @code{mlet}, except that the return values of the
  2241. monadic expressions are ignored. In that sense, it is analogous to
  2242. @code{begin}, but applied to monadic expressions.
  2243. @end deffn
  2244. @cindex state monad
  2245. The @code{(guix monads)} module provides the @dfn{state monad}, which
  2246. allows an additional value---the state---to be @emph{threaded} through
  2247. monadic procedure calls.
  2248. @defvr {Scheme Variable} %state-monad
  2249. The state monad. Procedures in the state monad can access and change
  2250. the state that is threaded.
  2251. Consider the example below. The @code{square} procedure returns a value
  2252. in the state monad. It returns the square of its argument, but also
  2253. increments the current state value:
  2254. @example
  2255. (define (square x)
  2256. (mlet %state-monad ((count (current-state)))
  2257. (mbegin %state-monad
  2258. (set-current-state (+ 1 count))
  2259. (return (* x x)))))
  2260. (run-with-state (sequence %state-monad (map square (iota 3))) 0)
  2261. @result{} (0 1 4)
  2262. @result{} 3
  2263. @end example
  2264. When ``run'' through @var{%state-monad}, we obtain that additional state
  2265. value, which is the number of @code{square} calls.
  2266. @end defvr
  2267. @deffn {Monadic Procedure} current-state
  2268. Return the current state as a monadic value.
  2269. @end deffn
  2270. @deffn {Monadic Procedure} set-current-state @var{value}
  2271. Set the current state to @var{value} and return the previous state as a
  2272. monadic value.
  2273. @end deffn
  2274. @deffn {Monadic Procedure} state-push @var{value}
  2275. Push @var{value} to the current state, which is assumed to be a list,
  2276. and return the previous state as a monadic value.
  2277. @end deffn
  2278. @deffn {Monadic Procedure} state-pop
  2279. Pop a value from the current state and return it as a monadic value.
  2280. The state is assumed to be a list.
  2281. @end deffn
  2282. @deffn {Scheme Procedure} run-with-state @var{mval} [@var{state}]
  2283. Run monadic value @var{mval} starting with @var{state} as the initial
  2284. state. Return two values: the resulting value, and the resulting state.
  2285. @end deffn
  2286. The main interface to the store monad, provided by the @code{(guix
  2287. store)} module, is as follows.
  2288. @defvr {Scheme Variable} %store-monad
  2289. The store monad---an alias for @var{%state-monad}.
  2290. Values in the store monad encapsulate accesses to the store. When its
  2291. effect is needed, a value of the store monad must be ``evaluated'' by
  2292. passing it to the @code{run-with-store} procedure (see below.)
  2293. @end defvr
  2294. @deffn {Scheme Procedure} run-with-store @var{store} @var{mval} [#:guile-for-build] [#:system (%current-system)]
  2295. Run @var{mval}, a monadic value in the store monad, in @var{store}, an
  2296. open store connection.
  2297. @end deffn
  2298. @deffn {Monadic Procedure} text-file @var{name} @var{text} [@var{references}]
  2299. Return as a monadic value the absolute file name in the store of the file
  2300. containing @var{text}, a string. @var{references} is a list of store items that the
  2301. resulting text file refers to; it defaults to the empty list.
  2302. @end deffn
  2303. @deffn {Monadic Procedure} interned-file @var{file} [@var{name}] @
  2304. [#:recursive? #t]
  2305. Return the name of @var{file} once interned in the store. Use
  2306. @var{name} as its store name, or the basename of @var{file} if
  2307. @var{name} is omitted.
  2308. When @var{recursive?} is true, the contents of @var{file} are added
  2309. recursively; if @var{file} designates a flat file and @var{recursive?}
  2310. is true, its contents are added, and its permission bits are kept.
  2311. The example below adds a file to the store, under two different names:
  2312. @example
  2313. (run-with-store (open-connection)
  2314. (mlet %store-monad ((a (interned-file "README"))
  2315. (b (interned-file "README" "LEGU-MIN")))
  2316. (return (list a b))))
  2317. @result{} ("/gnu/store/rwm@dots{}-README" "/gnu/store/44i@dots{}-LEGU-MIN")
  2318. @end example
  2319. @end deffn
  2320. The @code{(guix packages)} module exports the following package-related
  2321. monadic procedures:
  2322. @deffn {Monadic Procedure} package-file @var{package} [@var{file}] @
  2323. [#:system (%current-system)] [#:target #f] @
  2324. [#:output "out"] Return as a monadic
  2325. value in the absolute file name of @var{file} within the @var{output}
  2326. directory of @var{package}. When @var{file} is omitted, return the name
  2327. of the @var{output} directory of @var{package}. When @var{target} is
  2328. true, use it as a cross-compilation target triplet.
  2329. @end deffn
  2330. @deffn {Monadic Procedure} package->derivation @var{package} [@var{system}]
  2331. @deffnx {Monadic Procedure} package->cross-derivation @var{package} @
  2332. @var{target} [@var{system}]
  2333. Monadic version of @code{package-derivation} and
  2334. @code{package-cross-derivation} (@pxref{Defining Packages}).
  2335. @end deffn
  2336. @node G-Expressions
  2337. @section G-Expressions
  2338. @cindex G-expression
  2339. @cindex build code quoting
  2340. So we have ``derivations'', which represent a sequence of build actions
  2341. to be performed to produce an item in the store (@pxref{Derivations}).
  2342. Those build actions are performed when asking the daemon to actually
  2343. build the derivations; they are run by the daemon in a container
  2344. (@pxref{Invoking guix-daemon}).
  2345. @cindex strata of code
  2346. It should come as no surprise that we like to write those build actions
  2347. in Scheme. When we do that, we end up with two @dfn{strata} of Scheme
  2348. code@footnote{The term @dfn{stratum} in this context was coined by
  2349. Manuel Serrano et al.@: in the context of their work on Hop. Oleg
  2350. Kiselyov, who has written insightful
  2351. @url{, essays and code
  2352. on this topic}, refers to this kind of code generation as
  2353. @dfn{staging}.}: the ``host code''---code that defines packages, talks
  2354. to the daemon, etc.---and the ``build code''---code that actually
  2355. performs build actions, such as making directories, invoking
  2356. @command{make}, etc.
  2357. To describe a derivation and its build actions, one typically needs to
  2358. embed build code inside host code. It boils down to manipulating build
  2359. code as data, and Scheme's homoiconicity---code has a direct
  2360. representation as data---comes in handy for that. But we need more than
  2361. Scheme's normal @code{quasiquote} mechanism to construct build
  2362. expressions.
  2363. The @code{(guix gexp)} module implements @dfn{G-expressions}, a form of
  2364. S-expressions adapted to build expressions. G-expressions, or
  2365. @dfn{gexps}, consist essentially in three syntactic forms: @code{gexp},
  2366. @code{ungexp}, and @code{ungexp-splicing} (or simply: @code{#~},
  2367. @code{#$}, and @code{#$@@}), which are comparable respectively to
  2368. @code{quasiquote}, @code{unquote}, and @code{unquote-splicing}
  2369. (@pxref{Expression Syntax, @code{quasiquote},, guile, GNU Guile
  2370. Reference Manual}). However, there are major differences:
  2371. @itemize
  2372. @item
  2373. Gexps are meant to be written to a file and run or manipulated by other
  2374. processes.
  2375. @item
  2376. When a high-level object such as a package or derivation is unquoted
  2377. inside a gexp, the result is as if its output file name had been
  2378. introduced.
  2379. @item
  2380. Gexps carry information about the packages or derivations they refer to,
  2381. and these dependencies are automatically added as inputs to the build
  2382. processes that use them.
  2383. @end itemize
  2384. This mechanism is not limited to package and derivation
  2385. objects: @dfn{compilers} able to ``lower'' other high-level objects to
  2386. derivations can be defined, such that these objects can also be inserted
  2387. into gexps. For example, a useful type of high-level object that can be
  2388. inserted in a gexp is ``file-like objects'', which make it easy to
  2389. add files to the store and refer to them in
  2390. derivations and such (see @code{local-file} and @code{plain-file}
  2391. below.)
  2392. To illustrate the idea, here is an example of a gexp:
  2393. @example
  2394. (define build-exp
  2395. #~(begin
  2396. (mkdir #$output)
  2397. (chdir #$output)
  2398. (symlink (string-append #$coreutils "/bin/ls")
  2399. "list-files")))
  2400. @end example
  2401. This gexp can be passed to @code{gexp->derivation}; we obtain a
  2402. derivation that builds a directory containing exactly one symlink to
  2403. @file{/gnu/store/@dots{}-coreutils-8.22/bin/ls}:
  2404. @example
  2405. (gexp->derivation "the-thing" build-exp)
  2406. @end example
  2407. As one would expect, the @code{"/gnu/store/@dots{}-coreutils-8.22"} string is
  2408. substituted to the reference to the @var{coreutils} package in the
  2409. actual build code, and @var{coreutils} is automatically made an input to
  2410. the derivation. Likewise, @code{#$output} (equivalent to @code{(ungexp
  2411. output)}) is replaced by a string containing the derivation's output
  2412. directory name.
  2413. @cindex cross compilation
  2414. In a cross-compilation context, it is useful to distinguish between
  2415. references to the @emph{native} build of a package---that can run on the
  2416. host---versus references to cross builds of a package. To that end, the
  2417. @code{#+} plays the same role as @code{#$}, but is a reference to a
  2418. native package build:
  2419. @example
  2420. (gexp->derivation "vi"
  2421. #~(begin
  2422. (mkdir #$output)
  2423. (system* (string-append #+coreutils "/bin/ln")
  2424. "-s"
  2425. (string-append #$emacs "/bin/emacs")
  2426. (string-append #$output "/bin/vi")))
  2427. #:target "mips64el-linux")
  2428. @end example
  2429. @noindent
  2430. In the example above, the native build of @var{coreutils} is used, so
  2431. that @command{ln} can actually run on the host; but then the
  2432. cross-compiled build of @var{emacs} is referenced.
  2433. The syntactic form to construct gexps is summarized below.
  2434. @deffn {Scheme Syntax} #~@var{exp}
  2435. @deffnx {Scheme Syntax} (gexp @var{exp})
  2436. Return a G-expression containing @var{exp}. @var{exp} may contain one
  2437. or more of the following forms:
  2438. @table @code
  2439. @item #$@var{obj}
  2440. @itemx (ungexp @var{obj})
  2441. Introduce a reference to @var{obj}. @var{obj} may have one of the
  2442. supported types, for example a package or a
  2443. derivation, in which case the @code{ungexp} form is replaced by its
  2444. output file name---e.g., @code{"/gnu/store/@dots{}-coreutils-8.22}.
  2445. If @var{obj} is a list, it is traversed and references to supported
  2446. objects are substituted similarly.
  2447. If @var{obj} is another gexp, its contents are inserted and its
  2448. dependencies are added to those of the containing gexp.
  2449. If @var{obj} is another kind of object, it is inserted as is.
  2450. @item #$@var{obj}:@var{output}
  2451. @itemx (ungexp @var{obj} @var{output})
  2452. This is like the form above, but referring explicitly to the
  2453. @var{output} of @var{obj}---this is useful when @var{obj} produces
  2454. multiple outputs (@pxref{Packages with Multiple Outputs}).
  2455. @item #+@var{obj}
  2456. @itemx #+@var{obj}:output
  2457. @itemx (ungexp-native @var{obj})
  2458. @itemx (ungexp-native @var{obj} @var{output})
  2459. Same as @code{ungexp}, but produces a reference to the @emph{native}
  2460. build of @var{obj} when used in a cross compilation context.
  2461. @item #$output[:@var{output}]
  2462. @itemx (ungexp output [@var{output}])
  2463. Insert a reference to derivation output @var{output}, or to the main
  2464. output when @var{output} is omitted.
  2465. This only makes sense for gexps passed to @code{gexp->derivation}.
  2466. @item #$@@@var{lst}
  2467. @itemx (ungexp-splicing @var{lst})
  2468. Like the above, but splices the contents of @var{lst} inside the
  2469. containing list.
  2470. @item #+@@@var{lst}
  2471. @itemx (ungexp-native-splicing @var{lst})
  2472. Like the above, but refers to native builds of the objects listed in
  2473. @var{lst}.
  2474. @end table
  2475. G-expressions created by @code{gexp} or @code{#~} are run-time objects
  2476. of the @code{gexp?} type (see below.)
  2477. @end deffn
  2478. @deffn {Scheme Procedure} gexp? @var{obj}
  2479. Return @code{#t} if @var{obj} is a G-expression.
  2480. @end deffn
  2481. G-expressions are meant to be written to disk, either as code building
  2482. some derivation, or as plain files in the store. The monadic procedures
  2483. below allow you to do that (@pxref{The Store Monad}, for more
  2484. information about monads.)
  2485. @deffn {Monadic Procedure} gexp->derivation @var{name} @var{exp} @
  2486. [#:system (%current-system)] [#:target #f] [#:graft? #t] @
  2487. [#:hash #f] [#:hash-algo #f] @
  2488. [#:recursive? #f] [#:env-vars '()] [#:modules '()] @
  2489. [#:module-path @var{%load-path}] @
  2490. [#:references-graphs #f] [#:allowed-references #f] @
  2491. [#:leaked-env-vars #f] @
  2492. [#:local-build? #f] [#:guile-for-build #f]
  2493. Return a derivation @var{name} that runs @var{exp} (a gexp) with
  2494. @var{guile-for-build} (a derivation) on @var{system}. When @var{target}
  2495. is true, it is used as the cross-compilation target triplet for packages
  2496. referred to by @var{exp}.
  2497. Make @var{modules} available in the evaluation context of @var{exp};
  2498. @var{modules} is a list of names of Guile modules searched in
  2499. @var{module-path} to be copied in the store, compiled, and made available in
  2500. the load path during the execution of @var{exp}---e.g., @code{((guix
  2501. build utils) (guix build gnu-build-system))}.
  2502. @var{graft?} determines whether packages referred to by @var{exp} should be grafted when
  2503. applicable.
  2504. When @var{references-graphs} is true, it must be a list of tuples of one of the
  2505. following forms:
  2506. @example
  2507. (@var{file-name} @var{package})
  2508. (@var{file-name} @var{package} @var{output})
  2509. (@var{file-name} @var{derivation})
  2510. (@var{file-name} @var{derivation} @var{output})
  2511. (@var{file-name} @var{store-item})
  2512. @end example
  2513. The right-hand-side of each element of @var{references-graphs} is automatically made
  2514. an input of the build process of @var{exp}. In the build environment, each
  2515. @var{file-name} contains the reference graph of the corresponding item, in a simple
  2516. text format.
  2517. @var{allowed-references} must be either @code{#f} or a list of output names and packages.
  2518. In the latter case, the list denotes store items that the result is allowed to
  2519. refer to. Any reference to another store item will lead to a build error.
  2520. The other arguments are as for @code{derivation} (@pxref{Derivations}).
  2521. @end deffn
  2522. @cindex file-like objects
  2523. The @code{local-file} and @code{plain-file} procedures below return
  2524. @dfn{file-like objects}. That is, when unquoted in a G-expression,
  2525. these objects lead to a file in the store. Consider this G-expression:
  2526. @example
  2527. #~(system* (string-append #$glibc "/sbin/nscd") "-f"
  2528. #$(local-file "/tmp/my-nscd.conf"))
  2529. @end example
  2530. The effect here is to ``intern'' @file{/tmp/my-nscd.conf} by copying it
  2531. to the store. Once expanded, for instance @i{via}
  2532. @code{gexp->derivation}, the G-expression refers to that copy under
  2533. @file{/gnu/store}; thus, modifying or removing the file in @file{/tmp}
  2534. does not have any effect on what the G-expression does.
  2535. @code{plain-file} can be used similarly; it differs in that the file
  2536. content is directly passed as a string.
  2537. @deffn {Scheme Procedure} local-file @var{file} [@var{name}] @
  2538. [#:recursive? #t]
  2539. Return an object representing local file @var{file} to add to the store; this
  2540. object can be used in a gexp. @var{file} will be added to the store under @var{name}--by
  2541. default the base name of @var{file}.
  2542. When @var{recursive?} is true, the contents of @var{file} are added recursively; if @var{file}
  2543. designates a flat file and @var{recursive?} is true, its contents are added, and its
  2544. permission bits are kept.
  2545. This is the declarative counterpart of the @code{interned-file} monadic
  2546. procedure (@pxref{The Store Monad, @code{interned-file}}).
  2547. @end deffn
  2548. @deffn {Scheme Procedure} plain-file @var{name} @var{content}
  2549. Return an object representing a text file called @var{name} with the given
  2550. @var{content} (a string) to be added to the store.
  2551. This is the declarative counterpart of @code{text-file}.
  2552. @end deffn
  2553. @deffn {Monadic Procedure} gexp->script @var{name} @var{exp}
  2554. Return an executable script @var{name} that runs @var{exp} using
  2555. @var{guile} with @var{modules} in its search path.
  2556. The example below builds a script that simply invokes the @command{ls}
  2557. command:
  2558. @example
  2559. (use-modules (guix gexp) (gnu packages base))
  2560. (gexp->script "list-files"
  2561. #~(execl (string-append #$coreutils "/bin/ls")
  2562. "ls"))
  2563. @end example
  2564. When ``running'' it through the store (@pxref{The Store Monad,
  2565. @code{run-with-store}}), we obtain a derivation that produces an
  2566. executable file @file{/gnu/store/@dots{}-list-files} along these lines:
  2567. @example
  2568. #!/gnu/store/@dots{}-guile-2.0.11/bin/guile -ds
  2569. !#
  2570. (execl (string-append "/gnu/store/@dots{}-coreutils-8.22"/bin/ls")
  2571. "ls")
  2572. @end example
  2573. @end deffn
  2574. @deffn {Monadic Procedure} gexp->file @var{name} @var{exp}
  2575. Return a derivation that builds a file @var{name} containing @var{exp}.
  2576. The resulting file holds references to all the dependencies of @var{exp}
  2577. or a subset thereof.
  2578. @end deffn
  2579. @deffn {Monadic Procedure} text-file* @var{name} @var{text} @dots{}
  2580. Return as a monadic value a derivation that builds a text file
  2581. containing all of @var{text}. @var{text} may list, in addition to
  2582. strings, objects of any type that can be used in a gexp: packages,
  2583. derivations, local file objects, etc. The resulting store file holds
  2584. references to all these.
  2585. This variant should be preferred over @code{text-file} anytime the file
  2586. to create will reference items from the store. This is typically the
  2587. case when building a configuration file that embeds store file names,
  2588. like this:
  2589. @example
  2590. (define (
  2591. ;; Return the name of a shell script in the store that
  2592. ;; initializes the 'PATH' environment variable.
  2593. (text-file* ""
  2594. "export PATH=" coreutils "/bin:"
  2595. grep "/bin:" sed "/bin\n"))
  2596. @end example
  2597. In this example, the resulting @file{/gnu/store/@dots{}} file
  2598. will references @var{coreutils}, @var{grep}, and @var{sed}, thereby
  2599. preventing them from being garbage-collected during its lifetime.
  2600. @end deffn
  2601. Of course, in addition to gexps embedded in ``host'' code, there are
  2602. also modules containing build tools. To make it clear that they are
  2603. meant to be used in the build stratum, these modules are kept in the
  2604. @code{(guix build @dots{})} name space.
  2605. @c *********************************************************************
  2606. @node Utilities
  2607. @chapter Utilities
  2608. This section describes tools primarily targeted at developers and users
  2609. who write new package definitions. They complement the Scheme
  2610. programming interface of Guix in a convenient way.
  2611. @menu
  2612. * Invoking guix build:: Building packages from the command line.
  2613. * Invoking guix download:: Downloading a file and printing its hash.
  2614. * Invoking guix hash:: Computing the cryptographic hash of a file.
  2615. * Invoking guix import:: Importing package definitions.
  2616. * Invoking guix refresh:: Updating package definitions.
  2617. * Invoking guix lint:: Finding errors in package definitions.
  2618. * Invoking guix environment:: Setting up development environments.
  2619. * Invoking guix publish:: Sharing substitutes.
  2620. @end menu
  2621. @node Invoking guix build
  2622. @section Invoking @command{guix build}
  2623. The @command{guix build} command builds packages or derivations and
  2624. their dependencies, and prints the resulting store paths. Note that it
  2625. does not modify the user's profile---this is the job of the
  2626. @command{guix package} command (@pxref{Invoking guix package}). Thus,
  2627. it is mainly useful for distribution developers.
  2628. The general syntax is:
  2629. @example
  2630. guix build @var{options} @var{package-or-derivation}@dots{}
  2631. @end example
  2632. @var{package-or-derivation} may be either the name of a package found in
  2633. the software distribution such as @code{coreutils} or
  2634. @code{coreutils-8.20}, or a derivation such as
  2635. @file{/gnu/store/@dots{}-coreutils-8.19.drv}. In the former case, a
  2636. package with the corresponding name (and optionally version) is searched
  2637. for among the GNU distribution modules (@pxref{Package Modules}).
  2638. Alternatively, the @code{--expression} option may be used to specify a
  2639. Scheme expression that evaluates to a package; this is useful when
  2640. disambiguation among several same-named packages or package variants is
  2641. needed.
  2642. The @var{options} may be zero or more of the following:
  2643. @table @code
  2644. @item --expression=@var{expr}
  2645. @itemx -e @var{expr}
  2646. Build the package or derivation @var{expr} evaluates to.
  2647. For example, @var{expr} may be @code{(@@ (gnu packages guile)
  2648. guile-1.8)}, which unambiguously designates this specific variant of
  2649. version 1.8 of Guile.
  2650. Alternately, @var{expr} may be a G-expression, in which case it is used
  2651. as a build program passed to @code{gexp->derivation}
  2652. (@pxref{G-Expressions}).
  2653. Lastly, @var{expr} may refer to a zero-argument monadic procedure
  2654. (@pxref{The Store Monad}). The procedure must return a derivation as a
  2655. monadic value, which is then passed through @code{run-with-store}.
  2656. @item --source
  2657. @itemx -S
  2658. Build the packages' source derivations, rather than the packages
  2659. themselves.
  2660. For instance, @code{guix build -S gcc} returns something like
  2661. @file{/gnu/store/@dots{}-gcc-4.7.2.tar.bz2}, which is GCC's source tarball.
  2662. The returned source tarball is the result of applying any patches and
  2663. code snippets specified in the package's @code{origin} (@pxref{Defining
  2664. Packages}).
  2665. @item --sources
  2666. Fetch and return the source of @var{package-or-derivation} and all their
  2667. dependencies, recursively. This is a handy way to obtain a local copy
  2668. of all the source code needed to build @var{packages}, allowing you to
  2669. eventually build them even without network access. It is an extension
  2670. of the @code{--source} option and can accept one of the following
  2671. optional argument values:
  2672. @table @code
  2673. @item package
  2674. This value causes the @code{--sources} option to behave in the same way
  2675. as the @code{--source} option.
  2676. @item all
  2677. Build all packages' source derivations, including any source that might
  2678. be listed as @code{inputs}. This is the default value.
  2679. @example
  2680. $ guix build --sources tzdata
  2681. The following derivations will be built:
  2682. /gnu/store/@dots{}-tzdata2015b.tar.gz.drv
  2683. /gnu/store/@dots{}-tzcode2015b.tar.gz.drv
  2684. @end example
  2685. @item transitive
  2686. Build all packages' source derivations, as well as all source
  2687. derivations for packages' transitive inputs. This can be used e.g. to
  2688. prefetch package source for later offline building.
  2689. @example
  2690. $ guix build --sources=transitive tzdata
  2691. The following derivations will be built:
  2692. /gnu/store/@dots{}-tzcode2015b.tar.gz.drv
  2693. /gnu/store/@dots{}-findutils-4.4.2.tar.xz.drv
  2694. /gnu/store/@dots{}-grep-2.21.tar.xz.drv
  2695. /gnu/store/@dots{}-coreutils-8.23.tar.xz.drv
  2696. /gnu/store/@dots{}-make-4.1.tar.xz.drv
  2697. /gnu/store/@dots{}-bash-4.3.tar.xz.drv
  2698. @dots{}
  2699. @end example
  2700. @end table
  2701. @item --system=@var{system}
  2702. @itemx -s @var{system}
  2703. Attempt to build for @var{system}---e.g., @code{i686-linux}---instead of
  2704. the host's system type.
  2705. An example use of this is on Linux-based systems, which can emulate
  2706. different personalities. For instance, passing
  2707. @code{--system=i686-linux} on an @code{x86_64-linux} system allows users
  2708. to build packages in a complete 32-bit environment.
  2709. @item --target=@var{triplet}
  2710. @cindex cross-compilation
  2711. Cross-build for @var{triplet}, which must be a valid GNU triplet, such
  2712. as @code{"mips64el-linux-gnu"} (@pxref{Configuration Names, GNU
  2713. configuration triplets,, configure, GNU Configure and Build System}).
  2714. @item --with-source=@var{source}
  2715. Use @var{source} as the source of the corresponding package.
  2716. @var{source} must be a file name or a URL, as for @command{guix
  2717. download} (@pxref{Invoking guix download}).
  2718. The ``corresponding package'' is taken to be one specified on the
  2719. command line whose name matches the base of @var{source}---e.g., if
  2720. @var{source} is @code{/src/guile-2.0.10.tar.gz}, the corresponding
  2721. package is @code{guile}. Likewise, the version string is inferred from
  2722. @var{source}; in the previous example, it's @code{2.0.10}.
  2723. This option allows users to try out versions of packages other than the
  2724. one provided by the distribution. The example below downloads
  2725. @file{ed-1.7.tar.gz} from a GNU mirror and uses that as the source for
  2726. the @code{ed} package:
  2727. @example
  2728. guix build ed --with-source=mirror://gnu/ed/ed-1.7.tar.gz
  2729. @end example
  2730. As a developer, @code{--with-source} makes it easy to test release
  2731. candidates:
  2732. @example
  2733. guix build guile --with-source=../guile-
  2734. @end example
  2735. @dots{} or to build from a checkout in a pristine environment:
  2736. @example
  2737. $ git clone git://
  2738. $ guix build guix --with-source=./guix
  2739. @end example
  2740. @item --no-grafts
  2741. Do not ``graft'' packages. In practice, this means that package updates
  2742. available as grafts are not applied. @xref{Security Updates}, for more
  2743. information on grafts.
  2744. @item --derivations
  2745. @itemx -d
  2746. Return the derivation paths, not the output paths, of the given
  2747. packages.
  2748. @item --root=@var{file}
  2749. @itemx -r @var{file}
  2750. Make @var{file} a symlink to the result, and register it as a garbage
  2751. collector root.
  2752. @item --log-file
  2753. Return the build log file names for the given
  2754. @var{package-or-derivation}s, or raise an error if build logs are
  2755. missing.
  2756. This works regardless of how packages or derivations are specified. For
  2757. instance, the following invocations are equivalent:
  2758. @example
  2759. guix build --log-file `guix build -d guile`
  2760. guix build --log-file `guix build guile`
  2761. guix build --log-file guile
  2762. guix build --log-file -e '(@@ (gnu packages guile) guile-2.0)'
  2763. @end example
  2764. @end table
  2765. @cindex common build options
  2766. In addition, a number of options that control the build process are
  2767. common to @command{guix build} and other commands that can spawn builds,
  2768. such as @command{guix package} or @command{guix archive}. These are the
  2769. following:
  2770. @table @code
  2771. @item --load-path=@var{directory}
  2772. @itemx -L @var{directory}
  2773. Add @var{directory} to the front of the package module search path
  2774. (@pxref{Package Modules}).
  2775. This allows users to define their own packages and make them visible to
  2776. the command-line tools.
  2777. @item --keep-failed
  2778. @itemx -K
  2779. Keep the build tree of failed builds. Thus, if a build fail, its build
  2780. tree is kept under @file{/tmp}, in a directory whose name is shown at
  2781. the end of the build log. This is useful when debugging build issues.
  2782. @item --dry-run
  2783. @itemx -n
  2784. Do not build the derivations.
  2785. @item --fallback
  2786. When substituting a pre-built binary fails, fall back to building
  2787. packages locally.
  2788. @item --no-substitutes
  2789. Do not use substitutes for build products. That is, always build things
  2790. locally instead of allowing downloads of pre-built binaries
  2791. (@pxref{Substitutes}).
  2792. @item --no-build-hook
  2793. Do not attempt to offload builds @i{via} the daemon's ``build hook''
  2794. (@pxref{Daemon Offload Setup}). That is, always build things locally
  2795. instead of offloading builds to remote machines.
  2796. @item --max-silent-time=@var{seconds}
  2797. When the build or substitution process remains silent for more than
  2798. @var{seconds}, terminate it and report a build failure.
  2799. @item --timeout=@var{seconds}
  2800. Likewise, when the build or substitution process lasts for more than
  2801. @var{seconds}, terminate it and report a build failure.
  2802. By default there is no timeout. This behavior can be restored with
  2803. @code{--timeout=0}.
  2804. @item --verbosity=@var{level}
  2805. Use the given verbosity level. @var{level} must be an integer between 0
  2806. and 5; higher means more verbose output. Setting a level of 4 or more
  2807. may be helpful when debugging setup issues with the build daemon.
  2808. @item --cores=@var{n}
  2809. @itemx -c @var{n}
  2810. Allow the use of up to @var{n} CPU cores for the build. The special
  2811. value @code{0} means to use as many CPU cores as available.
  2812. @item --max-jobs=@var{n}
  2813. @itemx -M @var{n}
  2814. Allow at most @var{n} build jobs in parallel. @xref{Invoking
  2815. guix-daemon, @code{--max-jobs}}, for details about this option and the
  2816. equivalent @command{guix-daemon} option.
  2817. @end table
  2818. Behind the scenes, @command{guix build} is essentially an interface to
  2819. the @code{package-derivation} procedure of the @code{(guix packages)}
  2820. module, and to the @code{build-derivations} procedure of the @code{(guix
  2821. derivations)} module.
  2822. In addition to options explicitly passed on the command line,
  2823. @command{guix build} and other @command{guix} commands that support
  2824. building honor the @code{GUIX_BUILD_OPTIONS} environment variable.
  2825. @defvr {Environment Variable} GUIX_BUILD_OPTIONS
  2826. Users can define this variable to a list of command line options that
  2827. will automatically be used by @command{guix build} and other
  2828. @command{guix} commands that can perform builds, as in the example
  2829. below:
  2830. @example
  2831. $ export GUIX_BUILD_OPTIONS="--no-substitutes -c 2 -L /foo/bar"
  2832. @end example
  2833. These options are parsed independently, and the result is appended to
  2834. the parsed command-line options.
  2835. @end defvr
  2836. @node Invoking guix download
  2837. @section Invoking @command{guix download}
  2838. When writing a package definition, developers typically need to download
  2839. the package's source tarball, compute its SHA256 hash, and write that
  2840. hash in the package definition (@pxref{Defining Packages}). The
  2841. @command{guix download} tool helps with this task: it downloads a file
  2842. from the given URI, adds it to the store, and prints both its file name
  2843. in the store and its SHA256 hash.
  2844. The fact that the downloaded file is added to the store saves bandwidth:
  2845. when the developer eventually tries to build the newly defined package
  2846. with @command{guix build}, the source tarball will not have to be
  2847. downloaded again because it is already in the store. It is also a
  2848. convenient way to temporarily stash files, which may be deleted
  2849. eventually (@pxref{Invoking guix gc}).
  2850. The @command{guix download} command supports the same URIs as used in
  2851. package definitions. In particular, it supports @code{mirror://} URIs.
  2852. @code{https} URIs (HTTP over TLS) are supported @emph{provided} the
  2853. Guile bindings for GnuTLS are available in the user's environment; when
  2854. they are not available, an error is raised. @xref{Guile Preparations,
  2855. how to install the GnuTLS bindings for Guile,, gnutls-guile,
  2856. GnuTLS-Guile}, for more information.
  2857. The following option is available:
  2858. @table @code
  2859. @item --format=@var{fmt}
  2860. @itemx -f @var{fmt}
  2861. Write the hash in the format specified by @var{fmt}. For more
  2862. information on the valid values for @var{fmt}, @pxref{Invoking guix hash}.
  2863. @end table
  2864. @node Invoking guix hash
  2865. @section Invoking @command{guix hash}
  2866. The @command{guix hash} command computes the SHA256 hash of a file.
  2867. It is primarily a convenience tool for anyone contributing to the
  2868. distribution: it computes the cryptographic hash of a file, which can be
  2869. used in the definition of a package (@pxref{Defining Packages}).
  2870. The general syntax is:
  2871. @example
  2872. guix hash @var{option} @var{file}
  2873. @end example
  2874. @command{guix hash} has the following option:
  2875. @table @code
  2876. @item --format=@var{fmt}
  2877. @itemx -f @var{fmt}
  2878. Write the hash in the format specified by @var{fmt}.
  2879. Supported formats: @code{nix-base32}, @code{base32}, @code{base16}
  2880. (@code{hex} and @code{hexadecimal} can be used as well).
  2881. If the @option{--format} option is not specified, @command{guix hash}
  2882. will output the hash in @code{nix-base32}. This representation is used
  2883. in the definitions of packages.
  2884. @item --recursive
  2885. @itemx -r
  2886. Compute the hash on @var{file} recursively.
  2887. In this case, the hash is computed on an archive containing @var{file},
  2888. including its children if it is a directory. Some of @var{file}'s
  2889. meta-data is part of the archive; for instance, when @var{file} is a
  2890. regular file, the hash is different depending on whether @var{file} is
  2891. executable or not. Meta-data such as time stamps has no impact on the
  2892. hash (@pxref{Invoking guix archive}).
  2893. @c FIXME: Replace xref above with xref to an ``Archive'' section when
  2894. @c it exists.
  2895. @end table
  2896. @node Invoking guix import
  2897. @section Invoking @command{guix import}
  2898. @cindex importing packages
  2899. @cindex package import
  2900. @cindex package conversion
  2901. The @command{guix import} command is useful for people willing to add a
  2902. package to the distribution but who'd rather do as little work as
  2903. possible to get there---a legitimate demand. The command knows of a few
  2904. repositories from which it can ``import'' package meta-data. The result
  2905. is a package definition, or a template thereof, in the format we know
  2906. (@pxref{Defining Packages}).
  2907. The general syntax is:
  2908. @example
  2909. guix import @var{importer} @var{options}@dots{}
  2910. @end example
  2911. @var{importer} specifies the source from which to import package
  2912. meta-data, and @var{options} specifies a package identifier and other
  2913. options specific to @var{importer}. Currently, the available
  2914. ``importers'' are:
  2915. @table @code
  2916. @item gnu
  2917. Import meta-data for the given GNU package. This provides a template
  2918. for the latest version of that GNU package, including the hash of its
  2919. source tarball, and its canonical synopsis and description.
  2920. Additional information such as the package's dependencies and its
  2921. license needs to be figured out manually.
  2922. For example, the following command returns a package definition for
  2923. GNU@tie{}Hello:
  2924. @example
  2925. guix import gnu hello
  2926. @end example
  2927. Specific command-line options are:
  2928. @table @code
  2929. @item --key-download=@var{policy}
  2930. As for @code{guix refresh}, specify the policy to handle missing OpenPGP
  2931. keys when verifying the package's signature. @xref{Invoking guix
  2932. refresh, @code{--key-download}}.
  2933. @end table
  2934. @item pypi
  2935. @cindex pypi
  2936. Import meta-data from the @uref{, Python Package
  2937. Index}@footnote{This functionality requires Guile-JSON to be installed.
  2938. @xref{Requirements}.}. Information is taken from the JSON-formatted
  2939. description available at @code{} and usually includes all
  2940. the relevant information, including package dependencies.
  2941. The command below imports meta-data for the @code{itsdangerous} Python
  2942. package:
  2943. @example
  2944. guix import pypi itsdangerous
  2945. @end example
  2946. @item cpan
  2947. @cindex CPAN
  2948. Import meta-data from @uref{, MetaCPAN}.
  2949. Information is taken from the JSON-formatted meta-data provided through
  2950. @uref{, MetaCPAN's API} and includes most
  2951. relevant information, such as module dependencies. License information
  2952. should be checked closely. If Perl is available in the store, then the
  2953. @code{corelist} utility will be used to filter core modules out of the
  2954. list of dependencies.
  2955. The command command below imports meta-data for the @code{Acme::Boolean}
  2956. Perl module:
  2957. @example
  2958. guix import cpan Acme::Boolean
  2959. @end example
  2960. @item nix
  2961. Import meta-data from a local copy of the source of the
  2962. @uref{, Nixpkgs distribution}@footnote{This
  2963. relies on the @command{nix-instantiate} command of
  2964. @uref{, Nix}.}. Package definitions in Nixpkgs are
  2965. typically written in a mixture of Nix-language and Bash code. This
  2966. command only imports the high-level package structure that is written in
  2967. the Nix language. It normally includes all the basic fields of a
  2968. package definition.
  2969. When importing a GNU package, the synopsis and descriptions are replaced
  2970. by their canonical upstream variant.
  2971. As an example, the command below imports the package definition of
  2972. LibreOffice (more precisely, it imports the definition of the package
  2973. bound to the @code{libreoffice} top-level attribute):
  2974. @example
  2975. guix import nix ~/path/to/nixpkgs libreoffice
  2976. @end example
  2977. @item hackage
  2978. @cindex hackage
  2979. Import meta-data from Haskell community's central package archive
  2980. @uref{, Hackage}. Information is taken from
  2981. Cabal files and includes all the relevant information, including package
  2982. dependencies.
  2983. Specific command-line options are:
  2984. @table @code
  2985. @item --stdin
  2986. @itemx -s
  2987. Read a Cabal file from the standard input.
  2988. @item --no-test-dependencies
  2989. @itemx -t
  2990. Do not include dependencies required by the test suites only.
  2991. @item --cabal-environment=@var{alist}
  2992. @itemx -e @var{alist}
  2993. @var{alist} is a Scheme alist defining the environment in which the
  2994. Cabal conditionals are evaluated. The accepted keys are: @code{os},
  2995. @code{arch}, @code{impl} and a string representing the name of a flag.
  2996. The value associated with a flag has to be either the symbol
  2997. @code{true} or @code{false}. The value associated with other keys
  2998. has to conform to the Cabal file format definition. The default value
  2999. associated with the keys @code{os}, @code{arch} and @code{impl} is
  3000. @samp{linux}, @samp{x86_64} and @samp{ghc} respectively.
  3001. @end table
  3002. The command below imports meta-data for the latest version of the
  3003. @code{HTTP} Haskell package without including test dependencies and
  3004. specifying the value of the flag @samp{network-uri} as @code{false}:
  3005. @example
  3006. guix import hackage -t -e "'((\"network-uri\" . false))" HTTP
  3007. @end example
  3008. A specific package version may optionally be specified by following the
  3009. package name by a hyphen and a version number as in the following example:
  3010. @example
  3011. guix import hackage mtl-
  3012. @end example
  3013. @end table
  3014. The structure of the @command{guix import} code is modular. It would be
  3015. useful to have more importers for other package formats, and your help
  3016. is welcome here (@pxref{Contributing}).
  3017. @node Invoking guix refresh
  3018. @section Invoking @command{guix refresh}
  3019. The primary audience of the @command{guix refresh} command is developers
  3020. of the GNU software distribution. By default, it reports any packages
  3021. provided by the distribution that are outdated compared to the latest
  3022. upstream version, like this:
  3023. @example
  3024. $ guix refresh
  3025. gnu/packages/gettext.scm:29:13: gettext would be upgraded from to
  3026. gnu/packages/glib.scm:77:12: glib would be upgraded from 2.34.3 to 2.37.0
  3027. @end example
  3028. It does so by browsing each package's FTP directory and determining the
  3029. highest version number of the source tarballs
  3030. therein@footnote{Currently, this only works for GNU packages.}.
  3031. When passed @code{--update}, it modifies distribution source files to
  3032. update the version numbers and source tarball hashes of those packages'
  3033. recipes (@pxref{Defining Packages}). This is achieved by downloading
  3034. each package's latest source tarball and its associated OpenPGP
  3035. signature, authenticating the downloaded tarball against its signature
  3036. using @command{gpg}, and finally computing its hash. When the public
  3037. key used to sign the tarball is missing from the user's keyring, an
  3038. attempt is made to automatically retrieve it from a public key server;
  3039. when it's successful, the key is added to the user's keyring; otherwise,
  3040. @command{guix refresh} reports an error.
  3041. The following options are supported:
  3042. @table @code
  3043. @item --update
  3044. @itemx -u
  3045. Update distribution source files (package recipes) in place.
  3046. @xref{Defining Packages}, for more information on package definitions.
  3047. @item --select=[@var{subset}]
  3048. @itemx -s @var{subset}
  3049. Select all the packages in @var{subset}, one of @code{core} or
  3050. @code{non-core}.
  3051. The @code{core} subset refers to all the packages at the core of the
  3052. distribution---i.e., packages that are used to build ``everything
  3053. else''. This includes GCC, libc, Binutils, Bash, etc. Usually,
  3054. changing one of these packages in the distribution entails a rebuild of
  3055. all the others. Thus, such updates are an inconvenience to users in
  3056. terms of build time or bandwidth used to achieve the upgrade.
  3057. The @code{non-core} subset refers to the remaining packages. It is
  3058. typically useful in cases where an update of the core packages would be
  3059. inconvenient.
  3060. @end table
  3061. In addition, @command{guix refresh} can be passed one or more package
  3062. names, as in this example:
  3063. @example
  3064. guix refresh -u emacs idutils gcc-4.8.4
  3065. @end example
  3066. @noindent
  3067. The command above specifically updates the @code{emacs} and
  3068. @code{idutils} packages. The @code{--select} option would have no
  3069. effect in this case.
  3070. When considering whether to upgrade a package, it is sometimes
  3071. convenient to know which packages would be affected by the upgrade and
  3072. should be checked for compatibility. For this the following option may
  3073. be used when passing @command{guix refresh} one or more package names:
  3074. @table @code
  3075. @item --list-dependent
  3076. @itemx -l
  3077. List top-level dependent packages that would need to be rebuilt as a
  3078. result of upgrading one or more packages.
  3079. @end table
  3080. Be aware that the @code{--list-dependent} option only
  3081. @emph{approximates} the rebuilds that would be required as a result of
  3082. an upgrade. More rebuilds might be required under some circumstances.
  3083. @example
  3084. $ guix refresh --list-dependent flex
  3085. Building the following 120 packages would ensure 213 dependent packages are rebuilt:
  3086. hop-2.4.0 geiser-0.4 notmuch-0.18 mu- cflow-1.4 idutils-4.6 @dots{}
  3087. @end example
  3088. The command above lists a set of packages that could be built to check
  3089. for compatibility with an upgraded @code{flex} package.
  3090. The following options can be used to customize GnuPG operation:
  3091. @table @code
  3092. @item --gpg=@var{command}
  3093. Use @var{command} as the GnuPG 2.x command. @var{command} is searched
  3094. for in @code{$PATH}.
  3095. @item --key-download=@var{policy}
  3096. Handle missing OpenPGP keys according to @var{policy}, which may be one
  3097. of:
  3098. @table @code
  3099. @item always
  3100. Always download missing OpenPGP keys from the key server, and add them
  3101. to the user's GnuPG keyring.
  3102. @item never
  3103. Never try to download missing OpenPGP keys. Instead just bail out.
  3104. @item interactive
  3105. When a package signed with an unknown OpenPGP key is encountered, ask
  3106. the user whether to download it or not. This is the default behavior.
  3107. @end table
  3108. @item --key-server=@var{host}
  3109. Use @var{host} as the OpenPGP key server when importing a public key.
  3110. @end table
  3111. @node Invoking guix lint
  3112. @section Invoking @command{guix lint}
  3113. The @command{guix lint} is meant to help package developers avoid common
  3114. errors and use a consistent style. It runs a number of checks on a
  3115. given set of packages in order to find common mistakes in their
  3116. definitions. Available @dfn{checkers} include (see
  3117. @code{--list-checkers} for a complete list):
  3118. @table @code
  3119. @item synopsis
  3120. @itemx description
  3121. Validate certain typographical and stylistic rules about package
  3122. descriptions and synopses.
  3123. @item inputs-should-be-native
  3124. Identify inputs that should most likely be native inputs.
  3125. @item source
  3126. @itemx home-page
  3127. Probe @code{home-page} and @code{source} URLs and report those that are
  3128. invalid.
  3129. @end table
  3130. The general syntax is:
  3131. @example
  3132. guix lint @var{options} @var{package}@dots{}
  3133. @end example
  3134. If no package is given on the command line, then all packages are checked.
  3135. The @var{options} may be zero or more of the following:
  3136. @table @code
  3137. @item --checkers
  3138. @itemx -c
  3139. Only enable the checkers specified in a comma-separated list using the
  3140. names returned by @code{--list-checkers}.
  3141. @item --list-checkers
  3142. @itemx -l
  3143. List and describe all the available checkers that will be run on packages
  3144. and exit.
  3145. @end table
  3146. @node Invoking guix environment
  3147. @section Invoking @command{guix environment}
  3148. @cindex reproducible build environments
  3149. The purpose of @command{guix environment} is to assist hackers in
  3150. creating reproducible development environments without polluting their
  3151. package profile. The @command{guix environment} tool takes one or more
  3152. packages, builds all of the necessary inputs, and creates a shell
  3153. environment to use them.
  3154. The general syntax is:
  3155. @example
  3156. guix environment @var{options} @var{package}@dots{}
  3157. @end example
  3158. The following examples spawns a new shell that is capable of building
  3159. the GNU Guile source code:
  3160. @example
  3161. guix environment guile
  3162. @end example
  3163. If the specified packages are not built yet, @command{guix environment}
  3164. automatically builds them. The new shell's environment is an augmented
  3165. version of the environment that @command{guix environment} was run in.
  3166. It contains the necessary search paths for building the given package
  3167. added to the existing environment variables. To create a ``pure''
  3168. environment in which the original environment variables have been unset,
  3169. use the @code{--pure} option.
  3170. Additionally, more than one package may be specified, in which case the
  3171. union of the inputs for the given packages are used. For example, the
  3172. command below spawns a shell where all of the dependencies of both Guile
  3173. and Emacs are available:
  3174. @example
  3175. guix environment guile emacs
  3176. @end example
  3177. Sometimes an interactive shell session is not desired. The
  3178. @code{--exec} option can be used to specify the command to run instead.
  3179. @example
  3180. guix environment guile --exec=make
  3181. @end example
  3182. The following options are available:
  3183. @table @code
  3184. @item --expression=@var{expr}
  3185. @itemx -e @var{expr}
  3186. Create an environment for the package that @var{expr} evaluates to.
  3187. @item --load=@var{file}
  3188. @itemx -l @var{file}
  3189. Create an environment for the package that the code within @var{file}
  3190. evaluates to.
  3191. @item --exec=@var{command}
  3192. @item -E @var{command}
  3193. Execute @var{command} in the new environment.
  3194. @item --ad-hoc
  3195. Include all specified packages in the resulting environment, as if an
  3196. @i{ad hoc} package were defined with them as inputs. This option is
  3197. useful for quickly creating an environment without having to write a
  3198. package expression to contain the desired inputs.
  3199. For instance, the command:
  3200. @example
  3201. guix environment --ad-hoc guile guile-sdl -E guile
  3202. @end example
  3203. runs @command{guile} in an environment where Guile and Guile-SDL are
  3204. available.
  3205. @item --pure
  3206. Unset existing environment variables when building the new environment.
  3207. This has the effect of creating an environment in which search paths
  3208. only contain package inputs.
  3209. @item --search-paths
  3210. Display the environment variable definitions that make up the
  3211. environment.
  3212. @end table
  3213. It also supports all of the common build options that @command{guix
  3214. build} supports (@pxref{Invoking guix build, common build options}).
  3215. @node Invoking guix publish
  3216. @section Invoking @command{guix publish}
  3217. The purpose of @command{guix publish} is to enable users to easily share
  3218. their store with others, which can then use it as a substitute server
  3219. (@pxref{Substitutes}).
  3220. When @command{guix publish} runs, it spawns an HTTP server which allows
  3221. anyone with network access to obtain substitutes from it. This means
  3222. that any machine running Guix can also act as if it were a build farm,
  3223. since the HTTP interface is compatible with Hydra, the software behind
  3224. the @code{} build farm.
  3225. For security, each substitute is signed, allowing recipients to check
  3226. their authenticity and integrity (@pxref{Substitutes}). Because
  3227. @command{guix publish} uses the system's signing key, which is only
  3228. readable by the system administrator, it must be started as root; the
  3229. @code{--user} option makes it drop root privileges early on.
  3230. The general syntax is:
  3231. @example
  3232. guix publish @var{options}@dots{}
  3233. @end example
  3234. Running @command{guix publish} without any additional arguments will
  3235. spawn an HTTP server on port 8080:
  3236. @example
  3237. guix publish
  3238. @end example
  3239. Once a publishing server has been authorized (@pxref{Invoking guix
  3240. archive}), the daemon may download substitutes from it:
  3241. @example
  3242. guix-daemon --substitute-urls=
  3243. @end example
  3244. The following options are available:
  3245. @table @code
  3246. @item --port=@var{port}
  3247. @itemx -p @var{port}
  3248. Listen for HTTP requests on @var{port}.
  3249. @item --listen=@var{host}
  3250. Listen on the network interface for @var{host}. The default is to
  3251. accept connections from any interface.
  3252. @item --user=@var{user}
  3253. @itemx -u @var{user}
  3254. Change privileges to @var{user} as soon as possible---i.e., once the
  3255. server socket is open and the signing key has been read.
  3256. @item --repl[=@var{port}]
  3257. @itemx -r [@var{port}]
  3258. Spawn a Guile REPL server (@pxref{REPL Servers,,, guile, GNU Guile
  3259. Reference Manual}) on @var{port} (37146 by default). This is used
  3260. primarily for debugging a running @command{guix publish} server.
  3261. @end table
  3262. @c *********************************************************************
  3263. @node GNU Distribution
  3264. @chapter GNU Distribution
  3265. @cindex Guix System Distribution
  3266. @cindex GuixSD
  3267. Guix comes with a distribution of the GNU system consisting entirely of
  3268. free software@footnote{The term ``free'' here refers to the
  3269. @url{,freedom provided to
  3270. users of that software}.}. The
  3271. distribution can be installed on its own (@pxref{System Installation}),
  3272. but it is also possible to install Guix as a package manager on top of
  3273. an installed GNU/Linux system (@pxref{Installation}). To distinguish
  3274. between the two, we refer to the standalone distribution as the Guix
  3275. System Distribution, or GuixSD.
  3276. The distribution provides core GNU packages such as GNU libc, GCC, and
  3277. Binutils, as well as many GNU and non-GNU applications. The complete
  3278. list of available packages can be browsed
  3279. @url{,on-line} or by
  3280. running @command{guix package} (@pxref{Invoking guix package}):
  3281. @example
  3282. guix package --list-available
  3283. @end example
  3284. Our goal has been to provide a practical 100% free software distribution of
  3285. Linux-based and other variants of GNU, with a focus on the promotion and
  3286. tight integration of GNU components, and an emphasis on programs and
  3287. tools that help users exert that freedom.
  3288. Packages are currently available on the following platforms:
  3289. @table @code
  3290. @item x86_64-linux
  3291. Intel/AMD @code{x86_64} architecture, Linux-Libre kernel;
  3292. @item i686-linux
  3293. Intel 32-bit architecture (IA32), Linux-Libre kernel;
  3294. @item armhf-linux
  3295. ARMv7-A architecture with hard float, Thumb-2 and VFP3D16 coprocessor,
  3296. using the EABI hard-float ABI, and Linux-Libre kernel.
  3297. @item mips64el-linux
  3298. little-endian 64-bit MIPS processors, specifically the Loongson series,
  3299. n32 application binary interface (ABI), and Linux-Libre kernel.
  3300. @end table
  3301. GuixSD itself is currently only available on @code{i686} and @code{x86_64}.
  3302. @noindent
  3303. For information on porting to other architectures or kernels,
  3304. @xref{Porting}.
  3305. @menu
  3306. * System Installation:: Installing the whole operating system.
  3307. * System Configuration:: Configuring the operating system.
  3308. * Installing Debugging Files:: Feeding the debugger.
  3309. * Security Updates:: Deploying security fixes quickly.
  3310. * Package Modules:: Packages from the programmer's viewpoint.
  3311. * Packaging Guidelines:: Growing the distribution.
  3312. * Bootstrapping:: GNU/Linux built from scratch.
  3313. * Porting:: Targeting another platform or kernel.
  3314. @end menu
  3315. Building this distribution is a cooperative effort, and you are invited
  3316. to join! @xref{Contributing}, for information about how you can help.
  3317. @node System Installation
  3318. @section System Installation
  3319. @cindex Guix System Distribution
  3320. This section explains how to install the Guix System Distribution
  3321. on a machine. The Guix package manager can
  3322. also be installed on top of a running GNU/Linux system,
  3323. @pxref{Installation}.
  3324. @ifinfo
  3325. @c This paragraph is for people reading this from tty2 of the
  3326. @c installation image.
  3327. You're reading this documentation with an Info reader. For details on
  3328. how to use it, hit the @key{RET} key (``return'' or ``enter'') on the
  3329. link that follows: @pxref{Help,,, info, Info: An Introduction}. Hit
  3330. @kbd{l} afterwards to come back here.
  3331. @end ifinfo
  3332. @subsection Limitations
  3333. As of version @value{VERSION}, the Guix System Distribution (GuixSD) is
  3334. not production-ready. It may contain bugs and lack important
  3335. features. Thus, if you are looking for a stable production system that
  3336. respects your freedom as a computer user, a good solution at this point
  3337. is to consider @url{, one of
  3338. more established GNU/Linux distributions}. We hope you can soon switch
  3339. to the GuixSD without fear, of course. In the meantime, you can
  3340. also keep using your distribution and try out the package manager on top
  3341. of it (@pxref{Installation}).
  3342. Before you proceed with the installation, be aware of the following
  3343. noteworthy limitations applicable to version @value{VERSION}:
  3344. @itemize
  3345. @item
  3346. The installation process does not include a graphical user interface and
  3347. requires familiarity with GNU/Linux (see the following subsections to
  3348. get a feel of what that means.)
  3349. @item
  3350. The system does not yet provide GNOME and KDE; it provides Xfce, though,
  3351. if graphical desktop environments are your thing.
  3352. @item
  3353. Support for the Logical Volume Manager (LVM) is missing.
  3354. @item
  3355. Few system services are currently supported out-of-the-box
  3356. (@pxref{Services}).
  3357. @item
  3358. On the order of 1,900 packages are available, which means that you may
  3359. occasionally find that a useful package is missing.
  3360. @end itemize
  3361. You've been warned. But more than a disclaimer, this is an invitation
  3362. to report issues (and success stories!), and join us in improving it.
  3363. @xref{Contributing}, for more info.
  3364. @subsection USB Stick Installation
  3365. An installation image for USB sticks can be downloaded from
  3366. @indicateurl{{VERSION}.@var{system}.xz},
  3367. where @var{system} is one of:
  3368. @table @code
  3369. @item x86_64-linux
  3370. for a GNU/Linux system on Intel/AMD-compatible 64-bit CPUs;
  3371. @item i686-linux
  3372. for a 32-bit GNU/Linux system on Intel-compatible CPUs.
  3373. @end table
  3374. This image contains a single partition with the tools necessary for an
  3375. installation. It is meant to be copied @emph{as is} to a large-enough
  3376. USB stick.
  3377. To copy the image to a USB stick, follow these steps:
  3378. @enumerate
  3379. @item
  3380. Decompress the image using the @command{xz} command:
  3381. @example
  3382. xz -d guixsd-usb-install-@value{VERSION}.@var{system}.xz
  3383. @end example
  3384. @item
  3385. Insert a USB stick of 1@tie{}GiB or more in your machine, and determine
  3386. its device name. Assuming that USB stick is known as @file{/dev/sdX},
  3387. copy the image with:
  3388. @example
  3389. dd if=guixsd-usb-install-@value{VERSION}.x86_64 of=/dev/sdX
  3390. @end example
  3391. Access to @file{/dev/sdX} usually requires root privileges.
  3392. @end enumerate
  3393. Once this is done, you should be able to reboot the system and boot from
  3394. the USB stick. The latter usually requires you to get in the BIOS' boot
  3395. menu, where you can choose to boot from the USB stick.
  3396. @subsection Preparing for Installation
  3397. Once you have successfully booted the image on the USB stick, you should
  3398. end up with a root prompt. Several console TTYs are configured and can
  3399. be used to run commands as root. TTY2 shows this documentation,
  3400. browsable using the Info reader commands (@pxref{Help,,, info, Info: An
  3401. Introduction}).
  3402. To install the system, you would:
  3403. @enumerate
  3404. @item
  3405. Configure the network, by running @command{ifconfig eno1 up && dhclient
  3406. eno1} (to get an automatically assigned IP address from the wired
  3407. network interface controller@footnote{
  3408. @c
  3409. The name @code{eno1} is for the first on-board Ethernet controller. The
  3410. interface name for an Ethernet controller that is in the first slot of
  3411. the first PCI bus, for instance, would be @code{enp1s0}. Use
  3412. @command{ifconfig -a} to list all the available network interfaces.}),
  3413. or using the @command{ifconfig} command.
  3414. The system automatically loads drivers for your network interface
  3415. controllers.
  3416. Setting up network access is almost always a requirement because the
  3417. image does not contain all the software and tools that may be needed.
  3418. @item
  3419. Unless this has already been done, you must partition and format the
  3420. target partitions.
  3421. Preferably, assign partitions a label so that you can easily and
  3422. reliably refer to them in @code{file-system} declarations (@pxref{File
  3423. Systems}). This is typically done using the @code{-L} option of
  3424. @command{mkfs.ext4} and related commands.
  3425. The installation image includes Parted (@pxref{Overview,,, parted, GNU
  3426. Parted User Manual}), @command{fdisk}, Cryptsetup/LUKS for disk
  3427. encryption, and e2fsprogs, the suite of tools to manipulate
  3428. ext2/ext3/ext4 file systems.
  3429. @item
  3430. Once that is done, mount the target root partition under @file{/mnt}.
  3431. @item
  3432. Lastly, run @code{deco start cow-store /mnt}.
  3433. This will make @file{/gnu/store} copy-on-write, such that packages added
  3434. to it during the installation phase will be written to the target disk
  3435. rather than kept in memory.
  3436. @end enumerate
  3437. @subsection Proceeding with the Installation
  3438. With the target partitions ready, you now have to edit a file and
  3439. provide the declaration of the operating system to be installed. To
  3440. that end, the installation system comes with two text editors: GNU nano
  3441. (@pxref{Top,,, nano, GNU nano Manual}), and GNU Zile, an Emacs clone.
  3442. It is better to store that file on the target root file system, say, as
  3443. @file{/mnt/etc/config.scm}.
  3444. @xref{Using the Configuration System}, for examples of operating system
  3445. configurations. These examples are available under
  3446. @file{/etc/configuration} in the installation image, so you can copy
  3447. them and use them as a starting point for your own configuration.
  3448. Once you are done preparing the configuration file, the new system must
  3449. be initialized (remember that the target root file system is mounted
  3450. under @file{/mnt}):
  3451. @example
  3452. guix system init /mnt/etc/config.scm /mnt
  3453. @end example
  3454. @noindent
  3455. This will copy all the necessary files, and install GRUB on
  3456. @file{/dev/sdX}, unless you pass the @option{--no-grub} option. For
  3457. more information, @pxref{Invoking guix system}. This command may trigger
  3458. downloads or builds of missing packages, which can take some time.
  3459. Once that command has completed---and hopefully succeeded!---you can
  3460. run @command{reboot} and boot into the new system. Cross fingers, and
  3461. join us on @code{#guix} on the Freenode IRC network or on
  3462. @file{} to share your experience---good or not so
  3463. good.
  3464. @subsection Building the Installation Image
  3465. The installation image described above was built using the @command{guix
  3466. system} command, specifically:
  3467. @example
  3468. guix system disk-image --image-size=850MiB gnu/system/install.scm
  3469. @end example
  3470. @xref{Invoking guix system}, for more information. See
  3471. @file{gnu/system/install.scm} in the source tree for more information
  3472. about the installation image.
  3473. @node System Configuration
  3474. @section System Configuration
  3475. @cindex system configuration
  3476. The Guix System Distribution supports a consistent whole-system configuration
  3477. mechanism. By that we mean that all aspects of the global system
  3478. configuration---such as the available system services, timezone and
  3479. locale settings, user accounts---are declared in a single place. Such
  3480. a @dfn{system configuration} can be @dfn{instantiated}---i.e., effected.
  3481. One of the advantages of putting all the system configuration under the
  3482. control of Guix is that it supports transactional system upgrades, and
  3483. makes it possible to roll-back to a previous system instantiation,
  3484. should something go wrong with the new one (@pxref{Features}). Another
  3485. one is that it makes it easy to replicate the exact same configuration
  3486. across different machines, or at different points in time, without
  3487. having to resort to additional administration tools layered on top of
  3488. the system's own tools.
  3489. @c Yes, we're talking of Puppet, Chef, & co. here. ↑
  3490. This section describes this mechanism. First we focus on the system
  3491. administrator's viewpoint---explaining how the system is configured and
  3492. instantiated. Then we show how this mechanism can be extended, for
  3493. instance to support new system services.
  3494. @menu
  3495. * Using the Configuration System:: Customizing your GNU system.
  3496. * operating-system Reference:: Detail of operating-system declarations.
  3497. * File Systems:: Configuring file system mounts.
  3498. * Mapped Devices:: Block device extra processing.
  3499. * User Accounts:: Specifying user accounts.
  3500. * Locales:: Language and cultural convention settings.
  3501. * Services:: Specifying system services.
  3502. * Setuid Programs:: Programs running with root privileges.
  3503. * X.509 Certificates:: Authenticating HTTPS servers.
  3504. * Name Service Switch:: Configuring libc's name service switch.
  3505. * Initial RAM Disk:: Linux-Libre bootstrapping.
  3506. * GRUB Configuration:: Configuring the boot loader.
  3507. * Invoking guix system:: Instantiating a system configuration.
  3508. * Defining Services:: Adding new service definitions.
  3509. @end menu
  3510. @node Using the Configuration System
  3511. @subsection Using the Configuration System
  3512. The operating system is configured by providing an
  3513. @code{operating-system} declaration in a file that can then be passed to
  3514. the @command{guix system} command (@pxref{Invoking guix system}). A
  3515. simple setup, with the default system services, the default Linux-Libre
  3516. kernel, initial RAM disk, and boot loader looks like this:
  3517. @findex operating-system
  3518. @lisp
  3519. @include os-config-bare-bones.texi
  3520. @end lisp
  3521. This example should be self-describing. Some of the fields defined
  3522. above, such as @code{host-name} and @code{bootloader}, are mandatory.
  3523. Others, such as @code{packages} and @code{services}, can be omitted, in
  3524. which case they get a default value.
  3525. @vindex %base-packages
  3526. The @code{packages} field lists
  3527. packages that will be globally visible on the system, for all user
  3528. accounts---i.e., in every user's @code{PATH} environment variable---in
  3529. addition to the per-user profiles (@pxref{Invoking guix package}). The
  3530. @var{%base-packages} variable provides all the tools one would expect
  3531. for basic user and administrator tasks---including the GNU Core
  3532. Utilities, the GNU Networking Utilities, the GNU Zile lightweight text
  3533. editor, @command{find}, @command{grep}, etc. The example above adds
  3534. Emacs to those, taken from the @code{(gnu packages emacs)} module
  3535. (@pxref{Package Modules}).
  3536. @vindex %base-services
  3537. The @code{services} field lists @dfn{system services} to be made
  3538. available when the system starts (@pxref{Services}).
  3539. The @code{operating-system} declaration above specifies that, in
  3540. addition to the basic services, we want the @command{lshd} secure shell
  3541. daemon listening on port 2222, and allowing remote @code{root} logins
  3542. (@pxref{Invoking lshd,,, lsh, GNU lsh Manual}). Under the hood,
  3543. @code{lsh-service} arranges so that @code{lshd} is started with the
  3544. right command-line options, possibly with supporting configuration files
  3545. generated as needed (@pxref{Defining Services}). @xref{operating-system
  3546. Reference}, for details about the available @code{operating-system}
  3547. fields.
  3548. The configuration for a typical ``desktop'' usage, with the X11 display
  3549. server, a desktop environment, network management, an SSH server, and
  3550. more, would look like this:
  3551. @lisp
  3552. @include os-config-desktop.texi
  3553. @end lisp
  3554. @xref{Desktop Services}, for the exact list of services provided by
  3555. @var{%desktop-services}. @xref{X.509 Certificates}, for background
  3556. information about the @code{nss-certs} package that is used here.
  3557. Assuming the above snippet is stored in the @file{my-system-config.scm}
  3558. file, the @command{guix system reconfigure my-system-config.scm} command
  3559. instantiates that configuration, and makes it the default GRUB boot
  3560. entry (@pxref{Invoking guix system}). The normal way to change the
  3561. system's configuration is by updating this file and re-running the
  3562. @command{guix system} command.
  3563. At the Scheme level, the bulk of an @code{operating-system} declaration
  3564. is instantiated with the following monadic procedure (@pxref{The Store
  3565. Monad}):
  3566. @deffn {Monadic Procedure} operating-system-derivation os
  3567. Return a derivation that builds @var{os}, an @code{operating-system}
  3568. object (@pxref{Derivations}).
  3569. The output of the derivation is a single directory that refers to all
  3570. the packages, configuration files, and other supporting files needed to
  3571. instantiate @var{os}.
  3572. @end deffn
  3573. @node operating-system Reference
  3574. @subsection @code{operating-system} Reference
  3575. This section summarizes all the options available in
  3576. @code{operating-system} declarations (@pxref{Using the Configuration
  3577. System}).
  3578. @deftp {Data Type} operating-system
  3579. This is the data type representing an operating system configuration.
  3580. By that, we mean all the global system configuration, not per-user
  3581. configuration (@pxref{Using the Configuration System}).
  3582. @table @asis
  3583. @item @code{kernel} (default: @var{linux-libre})
  3584. The package object of the operating system kernel to use@footnote{Currently
  3585. only the Linux-libre kernel is supported. In the future, it will be
  3586. possible to use the GNU@tie{}Hurd.}.
  3587. @item @code{bootloader}
  3588. The system bootloader configuration object. @xref{GRUB Configuration}.
  3589. @item @code{initrd} (default: @code{base-initrd})
  3590. A two-argument monadic procedure that returns an initial RAM disk for
  3591. the Linux kernel. @xref{Initial RAM Disk}.
  3592. @item @code{firmware} (default: @var{%base-firmware})
  3593. @cindex firmware
  3594. List of firmware packages loadable by the operating system kernel.
  3595. The default includes firmware needed for Atheros-based WiFi devices
  3596. (Linux-libre module @code{ath9k}.)
  3597. @item @code{host-name}
  3598. The host name.
  3599. @item @code{hosts-file}
  3600. @cindex hosts file
  3601. A file-like object (@pxref{G-Expressions, file-like objects}) for use as
  3602. @file{/etc/hosts} (@pxref{Host Names,,, libc, The GNU C Library
  3603. Reference Manual}). The default is a file with entries for
  3604. @code{localhost} and @var{host-name}.
  3605. @item @code{mapped-devices} (default: @code{'()})
  3606. A list of mapped devices. @xref{Mapped Devices}.
  3607. @item @code{file-systems}
  3608. A list of file systems. @xref{File Systems}.
  3609. @item @code{swap-devices} (default: @code{'()})
  3610. @cindex swap devices
  3611. A list of strings identifying devices to be used for ``swap space''
  3612. (@pxref{Memory Concepts,,, libc, The GNU C Library Reference Manual}).
  3613. For example, @code{'("/dev/sda3")}.
  3614. @item @code{users} (default: @code{%base-user-accounts})
  3615. @itemx @code{groups} (default: @var{%base-groups})
  3616. List of user accounts and groups. @xref{User Accounts}.
  3617. @item @code{skeletons} (default: @code{(default-skeletons)})
  3618. A monadic list of pairs of target file name and files. These are the
  3619. files that will be used as skeletons as new accounts are created.
  3620. For instance, a valid value may look like this:
  3621. @example
  3622. (mlet %store-monad ((bashrc (text-file "bashrc" "\
  3623. export PATH=$HOME/.guix-profile/bin")))
  3624. (return `((".bashrc" ,bashrc))))
  3625. @end example
  3626. @item @code{issue} (default: @var{%default-issue})
  3627. A string denoting the contents of the @file{/etc/issue} file, which is
  3628. what displayed when users log in on a text console.
  3629. @item @code{packages} (default: @var{%base-packages})
  3630. The set of packages installed in the global profile, which is accessible
  3631. at @file{/run/current-system/profile}.
  3632. The default set includes core utilities, but it is good practice to
  3633. install non-core utilities in user profiles (@pxref{Invoking guix
  3634. package}).
  3635. @item @code{timezone}
  3636. A timezone identifying string---e.g., @code{"Europe/Paris"}.
  3637. @item @code{locale} (default: @code{"en_US.utf8"})
  3638. The name of the default locale (@pxref{Locale Names,,, libc, The GNU C
  3639. Library Reference Manual}). @xref{Locales}, for more information.
  3640. @item @code{locale-definitions} (default: @var{%default-locale-definitions})
  3641. The list of locale definitions to be compiled and that may be used at
  3642. run time. @xref{Locales}.
  3643. @item @code{name-service-switch} (default: @var{%default-nss})
  3644. Configuration of libc's name service switch (NSS)---a
  3645. @code{<name-service-switch>} object. @xref{Name Service Switch}, for
  3646. details.
  3647. @item @code{services} (default: @var{%base-services})
  3648. A list of monadic values denoting system services. @xref{Services}.
  3649. @item @code{pam-services} (default: @code{(base-pam-services)})
  3650. @cindex PAM
  3651. @cindex pluggable authentication modules
  3652. Linux @dfn{pluggable authentication module} (PAM) services.
  3653. @c FIXME: Add xref to PAM services section.
  3654. @item @code{setuid-programs} (default: @var{%setuid-programs})
  3655. List of string-valued G-expressions denoting setuid programs.
  3656. @xref{Setuid Programs}.
  3657. @item @code{sudoers} (default: @var{%sudoers-specification})
  3658. @cindex sudoers
  3659. The contents of the @file{/etc/sudoers} file as a file-like object
  3660. (@pxref{G-Expressions, @code{local-file} and @code{plain-file}}).
  3661. This file specifies which users can use the @command{sudo} command, what
  3662. they are allowed to do, and what privileges they may gain. The default
  3663. is that only @code{root} and members of the @code{wheel} group may use
  3664. @code{sudo}.
  3665. @end table
  3666. @end deftp
  3667. @node File Systems
  3668. @subsection File Systems
  3669. The list of file systems to be mounted is specified in the
  3670. @code{file-systems} field of the operating system's declaration
  3671. (@pxref{Using the Configuration System}). Each file system is declared
  3672. using the @code{file-system} form, like this:
  3673. @example
  3674. (file-system
  3675. (mount-point "/home")
  3676. (device "/dev/sda3")
  3677. (type "ext4"))
  3678. @end example
  3679. As usual, some of the fields are mandatory---those shown in the example
  3680. above---while others can be omitted. These are described below.
  3681. @deftp {Data Type} file-system
  3682. Objects of this type represent file systems to be mounted. They
  3683. contain the following members:
  3684. @table @asis
  3685. @item @code{type}
  3686. This is a string specifying the type of the file system---e.g.,
  3687. @code{"ext4"}.
  3688. @item @code{mount-point}
  3689. This designates the place where the file system is to be mounted.
  3690. @item @code{device}
  3691. This names the ``source'' of the file system. By default it is the name
  3692. of a node under @file{/dev}, but its meaning depends on the @code{title}
  3693. field described below.
  3694. @item @code{title} (default: @code{'device})
  3695. This is a symbol that specifies how the @code{device} field is to be
  3696. interpreted.
  3697. When it is the symbol @code{device}, then the @code{device} field is
  3698. interpreted as a file name; when it is @code{label}, then @code{device}
  3699. is interpreted as a partition label name; when it is @code{uuid},
  3700. @code{device} is interpreted as a partition unique identifier (UUID).
  3701. The @code{label} and @code{uuid} options offer a way to refer to disk
  3702. partitions without having to hard-code their actual device name.
  3703. However, when a file system's source is a mapped device (@pxref{Mapped
  3704. Devices}), its @code{device} field @emph{must} refer to the mapped
  3705. device name---e.g., @file{/dev/mapper/root-partition}---and consequently
  3706. @code{title} must be set to @code{'device}. This is required so that
  3707. the system knows that mounting the file system depends on having the
  3708. corresponding device mapping established.
  3709. @item @code{flags} (default: @code{'()})
  3710. This is a list of symbols denoting mount flags. Recognized flags
  3711. include @code{read-only}, @code{bind-mount}, @code{no-dev} (disallow
  3712. access to special files), @code{no-suid} (ignore setuid and setgid
  3713. bits), and @code{no-exec} (disallow program execution.)
  3714. @item @code{options} (default: @code{#f})
  3715. This is either @code{#f}, or a string denoting mount options.
  3716. @item @code{needed-for-boot?} (default: @code{#f})
  3717. This Boolean value indicates whether the file system is needed when
  3718. booting. If that is true, then the file system is mounted when the
  3719. initial RAM disk (initrd) is loaded. This is always the case, for
  3720. instance, for the root file system.
  3721. @item @code{check?} (default: @code{#t})
  3722. This Boolean indicates whether the file system needs to be checked for
  3723. errors before being mounted.
  3724. @item @code{create-mount-point?} (default: @code{#f})
  3725. When true, the mount point is created if it does not exist yet.
  3726. @end table
  3727. @end deftp
  3728. The @code{(gnu system file-systems)} exports the following useful
  3729. variables.
  3730. @defvr {Scheme Variable} %base-file-systems
  3731. These are essential file systems that are required on normal systems,
  3732. such as @var{%devtmpfs-file-system} and @var{%immutable-store} (see
  3733. below.) Operating system declarations should always contain at least
  3734. these.
  3735. @end defvr
  3736. @defvr {Scheme Variable} %devtmpfs-file-system
  3737. The @code{devtmpfs} file system to be mounted on @file{/dev}. This is a
  3738. requirement for udev (@pxref{Base Services, @code{udev-service}}).
  3739. @end defvr
  3740. @defvr {Scheme Variable} %pseudo-terminal-file-system
  3741. This is the file system to be mounted as @file{/dev/pts}. It supports
  3742. @dfn{pseudo-terminals} created @i{via} @code{openpty} and similar
  3743. functions (@pxref{Pseudo-Terminals,,, libc, The GNU C Library Reference
  3744. Manual}). Pseudo-terminals are used by terminal emulators such as
  3745. @command{xterm}.
  3746. @end defvr
  3747. @defvr {Scheme Variable} %shared-memory-file-system
  3748. This file system is mounted as @file{/dev/shm} and is used to support
  3749. memory sharing across processes (@pxref{Memory-mapped I/O,
  3750. @code{shm_open},, libc, The GNU C Library Reference Manual}).
  3751. @end defvr
  3752. @defvr {Scheme Variable} %immutable-store
  3753. This file system performs a read-only ``bind mount'' of
  3754. @file{/gnu/store}, making it read-only for all the users including
  3755. @code{root}. This prevents against accidental modification by software
  3756. running as @code{root} or by system administrators.
  3757. The daemon itself is still able to write to the store: it remounts it
  3758. read-write in its own ``name space.''
  3759. @end defvr
  3760. @defvr {Scheme Variable} %binary-format-file-system
  3761. The @code{binfmt_misc} file system, which allows handling of arbitrary
  3762. executable file types to be delegated to user space. This requires the
  3763. @code{binfmt.ko} kernel module to be loaded.
  3764. @end defvr
  3765. @defvr {Scheme Variable} %fuse-control-file-system
  3766. The @code{fusectl} file system, which allows unprivileged users to mount
  3767. and unmount user-space FUSE file systems. This requires the
  3768. @code{fuse.ko} kernel module to be loaded.
  3769. @end defvr
  3770. @node Mapped Devices
  3771. @subsection Mapped Devices
  3772. @cindex device mapping
  3773. @cindex mapped devices
  3774. The Linux kernel has a notion of @dfn{device mapping}: a block device,
  3775. such as a hard disk partition, can be @dfn{mapped} into another device,
  3776. with additional processing over the data that flows through
  3777. it@footnote{Note that the GNU@tie{}Hurd makes no difference between the
  3778. concept of a ``mapped device'' and that of a file system: both boil down
  3779. to @emph{translating} input/output operations made on a file to
  3780. operations on its backing store. Thus, the Hurd implements mapped
  3781. devices, like file systems, using the generic @dfn{translator} mechanism
  3782. (@pxref{Translators,,, hurd, The GNU Hurd Reference Manual}).}. A
  3783. typical example is encryption device mapping: all writes to the mapped
  3784. device are encrypted, and all reads are deciphered, transparently.
  3785. Mapped devices are declared using the @code{mapped-device} form:
  3786. @example
  3787. (mapped-device
  3788. (source "/dev/sda3")
  3789. (target "home")
  3790. (type luks-device-mapping))
  3791. @end example
  3792. @noindent
  3793. @cindex disk encryption
  3794. @cindex LUKS
  3795. This example specifies a mapping from @file{/dev/sda3} to
  3796. @file{/dev/mapper/home} using LUKS---the
  3797. @url{,Linux Unified Key Setup}, a
  3798. standard mechanism for disk encryption. The @file{/dev/mapper/home}
  3799. device can then be used as the @code{device} of a @code{file-system}
  3800. declaration (@pxref{File Systems}). The @code{mapped-device} form is
  3801. detailed below.
  3802. @deftp {Data Type} mapped-device
  3803. Objects of this type represent device mappings that will be made when
  3804. the system boots up.
  3805. @table @code
  3806. @item source
  3807. This string specifies the name of the block device to be mapped, such as
  3808. @code{"/dev/sda3"}.
  3809. @item target
  3810. This string specifies the name of the mapping to be established. For
  3811. example, specifying @code{"my-partition"} will lead to the creation of
  3812. the @code{"/dev/mapper/my-partition"} device.
  3813. @item type
  3814. This must be a @code{mapped-device-kind} object, which specifies how
  3815. @var{source} is mapped to @var{target}.
  3816. @end table
  3817. @end deftp
  3818. @defvr {Scheme Variable} luks-device-mapping
  3819. This defines LUKS block device encryption using the @command{cryptsetup}
  3820. command, from the same-named package. This relies on the
  3821. @code{dm-crypt} Linux kernel module.
  3822. @end defvr
  3823. @node User Accounts
  3824. @subsection User Accounts
  3825. User accounts and groups are entirely managed through the
  3826. @code{operating-system} declaration. They are specified with the
  3827. @code{user-account} and @code{user-group} forms:
  3828. @example
  3829. (user-account
  3830. (name "alice")
  3831. (group "users")
  3832. (supplementary-groups '("wheel" ;allow use of sudo, etc.
  3833. "audio" ;sound card
  3834. "video" ;video devices such as webcams
  3835. "cdrom")) ;the good ol' CD-ROM
  3836. (comment "Bob's sister")
  3837. (home-directory "/home/alice"))
  3838. @end example
  3839. When booting or upon completion of @command{guix system reconfigure},
  3840. the system ensures that only the user accounts and groups specified in
  3841. the @code{operating-system} declaration exist, and with the specified
  3842. properties. Thus, account or group creations or modifications made by
  3843. directly invoking commands such as @command{useradd} are lost upon
  3844. reconfiguration or reboot. This ensures that the system remains exactly
  3845. as declared.
  3846. @deftp {Data Type} user-account
  3847. Objects of this type represent user accounts. The following members may
  3848. be specified:
  3849. @table @asis
  3850. @item @code{name}
  3851. The name of the user account.
  3852. @item @code{group}
  3853. This is the name (a string) or identifier (a number) of the user group
  3854. this account belongs to.
  3855. @item @code{supplementary-groups} (default: @code{'()})
  3856. Optionally, this can be defined as a list of group names that this
  3857. account belongs to.
  3858. @item @code{uid} (default: @code{#f})
  3859. This is the user ID for this account (a number), or @code{#f}. In the
  3860. latter case, a number is automatically chosen by the system when the
  3861. account is created.
  3862. @item @code{comment} (default: @code{""})
  3863. A comment about the account, such as the account's owner full name.
  3864. @item @code{home-directory}
  3865. This is the name of the home directory for the account.
  3866. @item @code{shell} (default: Bash)
  3867. This is a G-expression denoting the file name of a program to be used as
  3868. the shell (@pxref{G-Expressions}).
  3869. @item @code{system?} (default: @code{#f})
  3870. This Boolean value indicates whether the account is a ``system''
  3871. account. System accounts are sometimes treated specially; for instance,
  3872. graphical login managers do not list them.
  3873. @item @code{password} (default: @code{#f})
  3874. You would normally leave this field to @code{#f}, initialize user
  3875. passwords as @code{root} with the @command{passwd} command, and then let
  3876. users change it with @command{passwd}. Passwords set with
  3877. @command{passwd} are of course preserved across reboot and
  3878. reconfiguration.
  3879. If you @emph{do} want to have a preset password for an account, then
  3880. this field must contain the encrypted password, as a string.
  3881. @xref{crypt,,, libc, The GNU C Library Reference Manual}, for more information
  3882. on password encryption, and @ref{Encryption,,, guile, GNU Guile Reference
  3883. Manual}, for information on Guile's @code{crypt} procedure.
  3884. @end table
  3885. @end deftp
  3886. User group declarations are even simpler:
  3887. @example
  3888. (user-group (name "students"))
  3889. @end example
  3890. @deftp {Data Type} user-group
  3891. This type is for, well, user groups. There are just a few fields:
  3892. @table @asis
  3893. @item @code{name}
  3894. The group's name.
  3895. @item @code{id} (default: @code{#f})
  3896. The group identifier (a number). If @code{#f}, a new number is
  3897. automatically allocated when the group is created.
  3898. @item @code{system?} (default: @code{#f})
  3899. This Boolean value indicates whether the group is a ``system'' group.
  3900. System groups have low numerical IDs.
  3901. @item @code{password} (default: @code{#f})
  3902. What, user groups can have a password? Well, apparently yes. Unless
  3903. @code{#f}, this field specifies the group's password.
  3904. @end table
  3905. @end deftp
  3906. For convenience, a variable lists all the basic user groups one may
  3907. expect:
  3908. @defvr {Scheme Variable} %base-groups
  3909. This is the list of basic user groups that users and/or packages expect
  3910. to be present on the system. This includes groups such as ``root'',
  3911. ``wheel'', and ``users'', as well as groups used to control access to
  3912. specific devices such as ``audio'', ``disk'', and ``cdrom''.
  3913. @end defvr
  3914. @defvr {Scheme Variable} %base-user-accounts
  3915. This is the list of basic system accounts that programs may expect to
  3916. find on a GNU/Linux system, such as the ``nobody'' account.
  3917. Note that the ``root'' account is not included here. It is a
  3918. special-case and is automatically added whether or not it is specified.
  3919. @end defvr
  3920. @node Locales
  3921. @subsection Locales
  3922. @cindex locale
  3923. A @dfn{locale} defines cultural conventions for a particular language
  3924. and region of the world (@pxref{Locales,,, libc, The GNU C Library
  3925. Reference Manual}). Each locale has a name that typically has the form
  3926. @code{@var{language}_@var{territory}.@var{charset}}---e.g.,
  3927. @code{fr_LU.utf8} designates the locale for the French language, with
  3928. cultural conventions from Luxembourg, and using the UTF-8 encoding.
  3929. @cindex locale definition
  3930. Usually, you will want to specify the default locale for the machine
  3931. using the @code{locale} field of the @code{operating-system} declaration
  3932. (@pxref{operating-system Reference, @code{locale}}).
  3933. That locale must be among the @dfn{locale definitions} that are known to
  3934. the system---and these are specified in the @code{locale-definitions}
  3935. slot of @code{operating-system}. The default value includes locale
  3936. definition for some widely used locales, but not for all the available
  3937. locales, in order to save space.
  3938. If the locale specified in the @code{locale} field is not among the
  3939. definitions listed in @code{locale-definitions}, @command{guix system}
  3940. raises an error. In that case, you should add the locale definition to
  3941. the @code{locale-definitions} field. For instance, to add the North
  3942. Frisian locale for Germany, the value of that field may be:
  3943. @example
  3944. (cons (locale-definition
  3945. (name "fy_DE.utf8") (source "fy_DE"))
  3946. %default-locale-definitions)
  3947. @end example
  3948. Likewise, to save space, one might want @code{locale-definitions} to
  3949. list only the locales that are actually used, as in:
  3950. @example
  3951. (list (locale-definition
  3952. (name "ja_JP.eucjp") (source "ja_JP")
  3953. (charset "EUC-JP")))
  3954. @end example
  3955. The @code{locale-definition} form is provided by the @code{(gnu system
  3956. locale)} module. Details are given below.
  3957. @deftp {Data Type} locale-definition
  3958. This is the data type of a locale definition.
  3959. @table @asis
  3960. @item @code{name}
  3961. The name of the locale. @xref{Locale Names,,, libc, The GNU C Library
  3962. Reference Manual}, for more information on locale names.
  3963. @item @code{source}
  3964. The name of the source for that locale. This is typically the
  3965. @code{@var{language}_@var{territory}} part of the locale name.
  3966. @item @code{charset} (default: @code{"UTF-8"})
  3967. The ``character set'' or ``code set'' for that locale,
  3968. @uref{, as defined by
  3969. IANA}.
  3970. @end table
  3971. @end deftp
  3972. @defvr {Scheme Variable} %default-locale-definitions
  3973. An arbitrary list of commonly used locales, used as the default value of
  3974. the @code{locale-definitions} field of @code{operating-system}
  3975. declarations.
  3976. @end defvr
  3977. @node Services
  3978. @subsection Services
  3979. @cindex system services
  3980. An important part of preparing an @code{operating-system} declaration is
  3981. listing @dfn{system services} and their configuration (@pxref{Using the
  3982. Configuration System}). System services are typically daemons launched
  3983. when the system boots, or other actions needed at that time---e.g.,
  3984. configuring network access.
  3985. Services are managed by GNU@tie{}dmd (@pxref{Introduction,,, dmd, GNU
  3986. dmd Manual}). On a running system, the @command{deco} command allows
  3987. you to list the available services, show their status, start and stop
  3988. them, or do other specific operations (@pxref{Jump Start,,, dmd, GNU dmd
  3989. Manual}). For example:
  3990. @example
  3991. # deco status dmd
  3992. @end example
  3993. The above command, run as @code{root}, lists the currently defined
  3994. services. The @command{deco doc} command shows a synopsis of the given
  3995. service:
  3996. @example
  3997. # deco doc nscd
  3998. Run libc's name service cache daemon (nscd).
  3999. @end example
  4000. The @command{start}, @command{stop}, and @command{restart} sub-commands
  4001. have the effect you would expect. For instance, the commands below stop
  4002. the nscd service and restart the Xorg display server:
  4003. @example
  4004. # deco stop nscd
  4005. Service nscd has been stopped.
  4006. # deco restart xorg-server
  4007. Service xorg-server has been stopped.
  4008. Service xorg-server has been started.
  4009. @end example
  4010. The following sections document the available services, starting with
  4011. the core services, that may be used in an @code{operating-system}
  4012. declaration.
  4013. @menu
  4014. * Base Services:: Essential system services.
  4015. * Networking Services:: Network setup, SSH daemon, etc.
  4016. * X Window:: Graphical display.
  4017. * Desktop Services:: D-Bus and desktop services.
  4018. * Database Services:: SQL databases.
  4019. * Various Services:: Other services.
  4020. @end menu
  4021. @node Base Services
  4022. @subsubsection Base Services
  4023. The @code{(gnu services base)} module provides definitions for the basic
  4024. services that one expects from the system. The services exported by
  4025. this module are listed below.
  4026. @defvr {Scheme Variable} %base-services
  4027. This variable contains a list of basic services@footnote{Technically,
  4028. this is a list of monadic services. @xref{The Store Monad}.} one would
  4029. expect from the system: a login service (mingetty) on each tty, syslogd,
  4030. libc's name service cache daemon (nscd), the udev device manager, and
  4031. more.
  4032. This is the default value of the @code{services} field of
  4033. @code{operating-system} declarations. Usually, when customizing a
  4034. system, you will want to append services to @var{%base-services}, like
  4035. this:
  4036. @example
  4037. (cons* (avahi-service) (lsh-service) %base-services)
  4038. @end example
  4039. @end defvr
  4040. @deffn {Monadic Procedure} host-name-service @var{name}
  4041. Return a service that sets the host name to @var{name}.
  4042. @end deffn
  4043. @deffn {Monadic Procedure} mingetty-service @var{tty} [#:motd] @
  4044. [#:auto-login #f] [#:login-program] [#:login-pause? #f] @
  4045. [#:allow-empty-passwords? #f]
  4046. Return a service to run mingetty on @var{tty}.
  4047. When @var{allow-empty-passwords?} is true, allow empty log-in password. When
  4048. @var{auto-login} is true, it must be a user name under which to log-in
  4049. automatically. @var{login-pause?} can be set to @code{#t} in conjunction with
  4050. @var{auto-login}, in which case the user will have to press a key before the
  4051. login shell is launched.
  4052. When true, @var{login-program} is a gexp or a monadic gexp denoting the name
  4053. of the log-in program (the default is the @code{login} program from the Shadow
  4054. tool suite.)
  4055. @var{motd} is a monadic value containing a text file to use as
  4056. the ``message of the day''.
  4057. @end deffn
  4058. @cindex name service cache daemon
  4059. @cindex nscd
  4060. @deffn {Monadic Procedure} nscd-service [@var{config}] [#:glibc glibc] @
  4061. [#:name-services '()]
  4062. Return a service that runs libc's name service cache daemon (nscd) with
  4063. the given @var{config}---an @code{<nscd-configuration>} object.
  4064. Optionally, @code{#:name-services} is a list of packages that provide
  4065. name service switch (NSS) modules needed by nscd. @xref{Name Service
  4066. Switch}, for an example.
  4067. @end deffn
  4068. @defvr {Scheme Variable} %nscd-default-configuration
  4069. This is the default @code{<nscd-configuration>} value (see below) used
  4070. by @code{nscd-service}. This uses the caches defined by
  4071. @var{%nscd-default-caches}; see below.
  4072. @end defvr
  4073. @deftp {Data Type} nscd-configuration
  4074. This is the type representing the name service cache daemon (nscd)
  4075. configuration.
  4076. @table @asis
  4077. @item @code{log-file} (default: @code{"/var/log/nscd.log"})
  4078. Name of nscd's log file. This is where debugging output goes when
  4079. @code{debug-level} is strictly positive.
  4080. @item @code{debug-level} (default: @code{0})
  4081. Integer denoting the debugging levels. Higher numbers mean more
  4082. debugging output is logged.
  4083. @item @code{caches} (default: @var{%nscd-default-caches})
  4084. List of @code{<nscd-cache>} objects denoting things to be cached; see
  4085. below.
  4086. @end table
  4087. @end deftp
  4088. @deftp {Data Type} nscd-cache
  4089. Data type representing a cache database of nscd and its parameters.
  4090. @table @asis
  4091. @item @code{database}
  4092. This is a symbol representing the name of the database to be cached.
  4093. Valid values are @code{passwd}, @code{group}, @code{hosts}, and
  4094. @code{services}, which designate the corresponding NSS database
  4095. (@pxref{NSS Basics,,, libc, The GNU C Library Reference Manual}).
  4096. @item @code{positive-time-to-live}
  4097. @itemx @code{negative-time-to-live} (default: @code{20})
  4098. A number representing the number of seconds during which a positive or
  4099. negative lookup result remains in cache.
  4100. @item @code{check-files?} (default: @code{#t})
  4101. Whether to check for updates of the files corresponding to
  4102. @var{database}.
  4103. For instance, when @var{database} is @code{hosts}, setting this flag
  4104. instructs nscd to check for updates in @file{/etc/hosts} and to take
  4105. them into account.
  4106. @item @code{persistent?} (default: @code{#t})
  4107. Whether the cache should be stored persistently on disk.
  4108. @item @code{shared?} (default: @code{#t})
  4109. Whether the cache should be shared among users.
  4110. @item @code{max-database-size} (default: 32@tie{}MiB)
  4111. Maximum size in bytes of the database cache.
  4112. @c XXX: 'suggested-size' and 'auto-propagate?' seem to be expert
  4113. @c settings, so leave them out.
  4114. @end table
  4115. @end deftp
  4116. @defvr {Scheme Variable} %nscd-default-caches
  4117. List of @code{<nscd-cache>} objects used by default by
  4118. @code{nscd-configuration} (see above.)
  4119. It enables persistent and aggressive caching of service and host name
  4120. lookups. The latter provides better host name lookup performance,
  4121. resilience in the face of unreliable name servers, and also better
  4122. privacy---often the result of host name lookups is in local cache, so
  4123. external name servers do not even need to be queried.
  4124. @end defvr
  4125. @deffn {Monadic Procedure} syslog-service [#:config-file #f]
  4126. Return a service that runs @code{syslogd}. If configuration file name
  4127. @var{config-file} is not specified, use some reasonable default
  4128. settings.
  4129. @end deffn
  4130. @deffn {Monadic Procedure} guix-service [#:guix guix] @
  4131. [#:builder-group "guixbuild"] [#:build-accounts 10] @
  4132. [#:authorize-hydra-key? #t] [#:use-substitutes? #t] @
  4133. [#:extra-options '()]
  4134. Return a service that runs the build daemon from @var{guix}, and has
  4135. @var{build-accounts} user accounts available under @var{builder-group}.
  4136. When @var{authorize-hydra-key?} is true, the @code{} public key
  4137. provided by @var{guix} is authorized upon activation, meaning that substitutes
  4138. from @code{} are used by default.
  4139. If @var{use-substitutes?} is false, the daemon is run with
  4140. @option{--no-substitutes} (@pxref{Invoking guix-daemon,
  4141. @option{--no-substitutes}}).
  4142. Finally, @var{extra-options} is a list of additional command-line options
  4143. passed to @command{guix-daemon}.
  4144. @end deffn
  4145. @deffn {Monadic Procedure} udev-service [#:udev udev]
  4146. Run @var{udev}, which populates the @file{/dev} directory dynamically.
  4147. @end deffn
  4148. @deffn {Monadic Procedure} console-keymap-service @var{file}
  4149. Return a service to load console keymap from @var{file} using
  4150. @command{loadkeys} command.
  4151. @end deffn
  4152. @node Networking Services
  4153. @subsubsection Networking Services
  4154. The @code{(gnu services networking)} module provides services to configure
  4155. the network interface.
  4156. @cindex DHCP, networking service
  4157. @deffn {Monadic Procedure} dhcp-client-service [#:dhcp @var{isc-dhcp}]
  4158. Return a service that runs @var{dhcp}, a Dynamic Host Configuration
  4159. Protocol (DHCP) client, on all the non-loopback network interfaces.
  4160. @end deffn
  4161. @deffn {Monadic Procedure} static-networking-service @var{interface} @var{ip} @
  4162. [#:gateway #f] [#:name-services @code{'()}]
  4163. Return a service that starts @var{interface} with address @var{ip}. If
  4164. @var{gateway} is true, it must be a string specifying the default network
  4165. gateway.
  4166. @end deffn
  4167. @cindex wicd
  4168. @deffn {Monadic Procedure} wicd-service [#:wicd @var{wicd}]
  4169. Return a service that runs @url{,Wicd}, a
  4170. network manager that aims to simplify wired and wireless networking.
  4171. @end deffn
  4172. @deffn {Monadic Procedure} ntp-service [#:ntp @var{ntp}] @
  4173. [#:name-service @var{%ntp-servers}]
  4174. Return a service that runs the daemon from @var{ntp}, the
  4175. @uref{, Network Time Protocol package}. The daemon will
  4176. keep the system clock synchronized with that of @var{servers}.
  4177. @end deffn
  4178. @defvr {Scheme Variable} %ntp-servers
  4179. List of host names used as the default NTP servers.
  4180. @end defvr
  4181. @deffn {Monadic Procedure} tor-service [#:tor tor]
  4182. Return a service to run the @uref{,Tor} daemon.
  4183. The daemon runs with the default settings (in particular the default exit
  4184. policy) as the @code{tor} unprivileged user.
  4185. @end deffn
  4186. @deffn {Monadic Procedure} bitlbee-service [#:bitlbee bitlbee] @
  4187. [#:interface ""] [#:port 6667] @
  4188. [#:extra-settings ""]
  4189. Return a service that runs @url{,BitlBee}, a daemon that
  4190. acts as a gateway between IRC and chat networks.
  4191. The daemon will listen to the interface corresponding to the IP address
  4192. specified in @var{interface}, on @var{port}. @code{} means that only
  4193. local clients can connect, whereas @code{} means that connections can
  4194. come from any networking interface.
  4195. In addition, @var{extra-settings} specifies a string to append to the
  4196. configuration file.
  4197. @end deffn
  4198. Furthermore, @code{(gnu services ssh)} provides the following service.
  4199. @deffn {Monadic Procedure} lsh-service [#:host-key "/etc/lsh/host-key"] @
  4200. [#:daemonic? #t] [#:interfaces '()] [#:port-number 22] @
  4201. [#:allow-empty-passwords? #f] [#:root-login? #f] @
  4202. [#:syslog-output? #t] [#:x11-forwarding? #t] @
  4203. [#:tcp/ip-forwarding? #t] [#:password-authentication? #t] @
  4204. [#:public-key-authentication? #t] [#:initialize? #t]
  4205. Run the @command{lshd} program from @var{lsh} to listen on port @var{port-number}.
  4206. @var{host-key} must designate a file containing the host key, and readable
  4207. only by root.
  4208. When @var{daemonic?} is true, @command{lshd} will detach from the
  4209. controlling terminal and log its output to syslogd, unless one sets
  4210. @var{syslog-output?} to false. Obviously, it also makes lsh-service
  4211. depend on existence of syslogd service. When @var{pid-file?} is true,
  4212. @command{lshd} writes its PID to the file called @var{pid-file}.
  4213. When @var{initialize?} is true, automatically create the seed and host key
  4214. upon service activation if they do not exist yet. This may take long and
  4215. require interaction.
  4216. When @var{initialize?} is false, it is up to the user to initialize the
  4217. randomness generator (@pxref{lsh-make-seed,,, lsh, LSH Manual}), and to create
  4218. a key pair with the private key stored in file @var{host-key} (@pxref{lshd
  4219. basics,,, lsh, LSH Manual}).
  4220. When @var{interfaces} is empty, lshd listens for connections on all the
  4221. network interfaces; otherwise, @var{interfaces} must be a list of host names
  4222. or addresses.
  4223. @var{allow-empty-passwords?} specifies whether to accept log-ins with empty
  4224. passwords, and @var{root-login?} specifies whether to accept log-ins as
  4225. root.
  4226. The other options should be self-descriptive.
  4227. @end deffn
  4228. @defvr {Scheme Variable} %facebook-host-aliases
  4229. This variable contains a string for use in @file{/etc/hosts}
  4230. (@pxref{Host Names,,, libc, The GNU C Library Reference Manual}). Each
  4231. line contains a entry that maps a known server name of the Facebook
  4232. on-line service---e.g., @code{}---to the local
  4233. host---@code{} or its IPv6 equivalent, @code{::1}.
  4234. This variable is typically used in the @code{hosts-file} field of an
  4235. @code{operating-system} declaration (@pxref{operating-system Reference,
  4236. @file{/etc/hosts}}):
  4237. @example
  4238. (use-modules (gnu) (guix))
  4239. (operating-system
  4240. (host-name "mymachine")
  4241. ;; ...
  4242. (hosts-file
  4243. ;; Create a /etc/hosts file with aliases for "localhost"
  4244. ;; and "mymachine", as well as for Facebook servers.
  4245. (plain-file "hosts"
  4246. (string-append (local-host-aliases host-name)
  4247. %facebook-host-aliases))))
  4248. @end example
  4249. This mechanism can prevent programs running locally, such as Web
  4250. browsers, from accessing Facebook.
  4251. @end defvr
  4252. The @code{(gnu services avahi)} provides the following definition.
  4253. @deffn {Monadic Procedure} avahi-service [#:avahi @var{avahi}] @
  4254. [#:host-name #f] [#:publish? #t] [#:ipv4? #t] @
  4255. [#:ipv6? #t] [#:wide-area? #f] @
  4256. [#:domains-to-browse '()]
  4257. Return a service that runs @command{avahi-daemon}, a system-wide
  4258. mDNS/DNS-SD responder that allows for service discovery and
  4259. "zero-configuration" host name lookups (see @uref{}).
  4260. If @var{host-name} is different from @code{#f}, use that as the host name to
  4261. publish for this machine; otherwise, use the machine's actual host name.
  4262. When @var{publish?} is true, publishing of host names and services is allowed;
  4263. in particular, avahi-daemon will publish the machine's host name and IP
  4264. address via mDNS on the local network.
  4265. When @var{wide-area?} is true, DNS-SD over unicast DNS is enabled.
  4266. Boolean values @var{ipv4?} and @var{ipv6?} determine whether to use IPv4/IPv6
  4267. sockets.
  4268. @end deffn
  4269. @node X Window
  4270. @subsubsection X Window
  4271. Support for the X Window graphical display system---specifically
  4272. Xorg---is provided by the @code{(gnu services xorg)} module. Note that
  4273. there is no @code{xorg-service} procedure. Instead, the X server is
  4274. started by the @dfn{login manager}, currently SLiM.
  4275. @deffn {Monadic Procedure} slim-service [#:allow-empty-passwords? #f] @
  4276. [#:auto-login? #f] [#:default-user ""] [#:startx] @
  4277. [#:theme @var{%default-slim-theme}] @
  4278. [#:theme-name @var{%default-slim-theme-name}]
  4279. Return a service that spawns the SLiM graphical login manager, which in
  4280. turn starts the X display server with @var{startx}, a command as returned by
  4281. @code{xorg-start-command}.
  4282. @cindex X session
  4283. SLiM automatically looks for session types described by the @file{.desktop}
  4284. files in @file{/run/current-system/profile/share/xsessions} and allows users
  4285. to choose a session from the log-in screen using @kbd{F1}. Packages such as
  4286. @var{xfce}, @var{sawfish}, and @var{ratpoison} provide @file{.desktop} files;
  4287. adding them to the system-wide set of packages automatically makes them
  4288. available at the log-in screen.
  4289. In addition, @file{~/.xsession} files are honored. When available,
  4290. @file{~/.xsession} must be an executable that starts a window manager
  4291. and/or other X clients.
  4292. When @var{allow-empty-passwords?} is true, allow logins with an empty
  4293. password. When @var{auto-login?} is true, log in automatically as
  4294. @var{default-user}.
  4295. If @var{theme} is @code{#f}, the use the default log-in theme; otherwise
  4296. @var{theme} must be a gexp denoting the name of a directory containing the
  4297. theme to use. In that case, @var{theme-name} specifies the name of the
  4298. theme.
  4299. @end deffn
  4300. @defvr {Scheme Variable} %default-theme
  4301. @defvrx {Scheme Variable} %default-theme-name
  4302. The G-Expression denoting the default SLiM theme and its name.
  4303. @end defvr
  4304. @deffn {Monadic Procedure} xorg-start-command [#:guile] @
  4305. [#:configuration-file #f] [#:xorg-server @var{xorg-server}]
  4306. Return a derivation that builds a @var{guile} script to start the X server
  4307. from @var{xorg-server}. @var{configuration-file} is the server configuration
  4308. file or a derivation that builds it; when omitted, the result of
  4309. @code{xorg-configuration-file} is used.
  4310. Usually the X server is started by a login manager.
  4311. @end deffn
  4312. @deffn {Monadic Procedure} xorg-configuration-file @
  4313. [#:drivers '()] [#:resolutions '()] [#:extra-config '()]
  4314. Return a configuration file for the Xorg server containing search paths for
  4315. all the common drivers.
  4316. @var{drivers} must be either the empty list, in which case Xorg chooses a
  4317. graphics driver automatically, or a list of driver names that will be tried in
  4318. this order---e.g., @code{(\"modesetting\" \"vesa\")}.
  4319. Likewise, when @var{resolutions} is the empty list, Xorg chooses an
  4320. appropriate screen resolution; otherwise, it must be a list of
  4321. resolutions---e.g., @code{((1024 768) (640 480))}.
  4322. Last, @var{extra-config} is a list of strings or objects appended to the
  4323. @code{text-file*} argument list. It is used to pass extra text to be added
  4324. verbatim to the configuration file.
  4325. @end deffn
  4326. @node Desktop Services
  4327. @subsubsection Desktop Services
  4328. The @code{(gnu services desktop)} module provides services that are
  4329. usually useful in the context of a ``desktop'' setup---that is, on a
  4330. machine running a graphical display server, possibly with graphical user
  4331. interfaces, etc.
  4332. To simplify things, the module defines a variable containing the set of
  4333. services that users typically expect on a machine with a graphical
  4334. environment and networking:
  4335. @defvr {Scheme Variable} %desktop-services
  4336. This is a list of services that builds upon @var{%base-services} and
  4337. adds or adjust services for a typical ``desktop'' setup.
  4338. In particular, it adds a graphical login manager (@pxref{X Window,
  4339. @code{slim-service}}), a network management tool (@pxref{Networking
  4340. Services, @code{wicd-service}}), energy and color management services,
  4341. an NTP client and an SSH server (@pxref{Networking Services}), the Avahi
  4342. daemon, and has the name service switch service configured to be able to
  4343. use @code{nss-mdns} (@pxref{Name Service Switch, mDNS}).
  4344. @end defvr
  4345. The @var{%desktop-services} variable can be used as the @code{services}
  4346. field of an @code{operating-system} declaration (@pxref{operating-system
  4347. Reference, @code{services}}).
  4348. The actual service definitions provided by @code{(gnu services desktop)}
  4349. are described below.
  4350. @deffn {Monadic Procedure} dbus-service @var{services} @
  4351. [#:dbus @var{dbus}]
  4352. Return a service that runs the ``system bus'', using @var{dbus}, with
  4353. support for @var{services}.
  4354. @uref{, D-Bus} is an inter-process communication
  4355. facility. Its system bus is used to allow system services to communicate
  4356. and be notified of system-wide events.
  4357. @var{services} must be a list of packages that provide an
  4358. @file{etc/dbus-1/system.d} directory containing additional D-Bus configuration
  4359. and policy files. For example, to allow avahi-daemon to use the system bus,
  4360. @var{services} must be equal to @code{(list avahi)}.
  4361. @end deffn
  4362. @deffn {Monadic Procedure} upower-service [#:upower @var{upower}] @
  4363. [#:watts-up-pro? #f] @
  4364. [#:poll-batteries? #t] @
  4365. [#:ignore-lid? #f] @
  4366. [#:use-percentage-for-policy? #f] @
  4367. [#:percentage-low 10] @
  4368. [#:percentage-critical 3] @
  4369. [#:percentage-action 2] @
  4370. [#:time-low 1200] @
  4371. [#:time-critical 300] @
  4372. [#:time-action 120] @
  4373. [#:critical-power-action 'hybrid-sleep]
  4374. Return a service that runs @uref{,
  4375. @command{upowerd}}, a system-wide monitor for power consumption and battery
  4376. levels, with the given configuration settings. It implements the
  4377. @code{org.freedesktop.UPower} D-Bus interface, and is notably used by
  4378. GNOME.
  4379. @end deffn
  4380. @deffn {Monadic Procedure} colord-service [#:colord @var{colord}]
  4381. Return a service that runs @command{colord}, a system service with a D-Bus
  4382. interface to manage the color profiles of input and output devices such as
  4383. screens and scanners. It is notably used by the GNOME Color Manager graphical
  4384. tool. See @uref{, the colord web
  4385. site} for more information.
  4386. @end deffn
  4387. @node Database Services
  4388. @subsubsection Database Services
  4389. The @code{(gnu services databases)} module provides the following service.
  4390. @deffn {Monadic Procedure} postgresql-service [#:postgresql postgresql] @
  4391. [#:config-file] [#:data-directory ``/var/lib/postgresql/data'']
  4392. Return a service that runs @var{postgresql}, the PostgreSQL database
  4393. server.
  4394. The PostgreSQL daemon loads its runtime configuration from
  4395. @var{config-file} and stores the database cluster in
  4396. @var{data-directory}.
  4397. @end deffn
  4398. @node Various Services
  4399. @subsubsection Various Services
  4400. The @code{(gnu services lirc)} module provides the following service.
  4401. @deffn {Monadic Procedure} lirc-service [#:lirc lirc] @
  4402. [#:device #f] [#:driver #f] [#:config-file #f] @
  4403. [#:extra-options '()]
  4404. Return a service that runs @url{,LIRC}, a daemon that
  4405. decodes infrared signals from remote controls.
  4406. Optionally, @var{device}, @var{driver} and @var{config-file}
  4407. (configuration file name) may be specified. See @command{lircd} manual
  4408. for details.
  4409. Finally, @var{extra-options} is a list of additional command-line options
  4410. passed to @command{lircd}.
  4411. @end deffn
  4412. @node Setuid Programs
  4413. @subsection Setuid Programs
  4414. @cindex setuid programs
  4415. Some programs need to run with ``root'' privileges, even when they are
  4416. launched by unprivileged users. A notorious example is the
  4417. @command{passwd} programs, which can users can run to change their
  4418. password, and which requires write access to the @file{/etc/passwd} and
  4419. @file{/etc/shadow} files---something normally restricted to root, for
  4420. obvious security reasons. To address that, these executables are
  4421. @dfn{setuid-root}, meaning that they always run with root privileges
  4422. (@pxref{How Change Persona,,, libc, The GNU C Library Reference Manual},
  4423. for more info about the setuid mechanisms.)
  4424. The store itself @emph{cannot} contain setuid programs: that would be a
  4425. security issue since any user on the system can write derivations that
  4426. populate the store (@pxref{The Store}). Thus, a different mechanism is
  4427. used: instead of changing the setuid bit directly on files that are in
  4428. the store, we let the system administrator @emph{declare} which programs
  4429. should be setuid root.
  4430. The @code{setuid-programs} field of an @code{operating-system}
  4431. declaration contains a list of G-expressions denoting the names of
  4432. programs to be setuid-root (@pxref{Using the Configuration System}).
  4433. For instance, the @command{passwd} program, which is part of the Shadow
  4434. package, can be designated by this G-expression (@pxref{G-Expressions}):
  4435. @example
  4436. #~(string-append #$shadow "/bin/passwd")
  4437. @end example
  4438. A default set of setuid programs is defined by the
  4439. @code{%setuid-programs} variable of the @code{(gnu system)} module.
  4440. @defvr {Scheme Variable} %setuid-programs
  4441. A list of G-expressions denoting common programs that are setuid-root.
  4442. The list includes commands such as @command{passwd}, @command{ping},
  4443. @command{su}, and @command{sudo}.
  4444. @end defvr
  4445. Under the hood, the actual setuid programs are created in the
  4446. @file{/run/setuid-programs} directory at system activation time. The
  4447. files in this directory refer to the ``real'' binaries, which are in the
  4448. store.
  4449. @node X.509 Certificates
  4450. @subsection X.509 Certificates
  4451. @cindex HTTPS, certificates
  4452. @cindex X.509 certificates
  4453. @cindex TLS
  4454. Web servers available over HTTPS (that is, HTTP over the transport-layer
  4455. security mechanism, TLS) send client programs an @dfn{X.509 certificate}
  4456. that the client can then use to @emph{authenticate} the server. To do
  4457. that, clients verify that the server's certificate is signed by a
  4458. so-called @dfn{certificate authority} (CA). But to verify the CA's
  4459. signature, clients must have first acquired the CA's certificate.
  4460. Web browsers such as GNU@tie{}IceCat include their own set of CA
  4461. certificates, such that they are able to verify CA signatures
  4462. out-of-the-box.
  4463. However, most other programs that can talk HTTPS---@command{wget},
  4464. @command{git}, @command{w3m}, etc.---need to be told where CA
  4465. certificates can be found.
  4466. @cindex @code{nss-certs}
  4467. In GuixSD, this is done by adding a package that provides certificates
  4468. to the @code{packages} field of the @code{operating-system} declaration
  4469. (@pxref{operating-system Reference}). GuixSD includes one such package,
  4470. @code{nss-certs}, which is a set of CA certificates provided as part of
  4471. Mozilla's Network Security Services.
  4472. Note that it is @emph{not} part of @var{%base-packages}, so you need to
  4473. explicitly add it. The @file{/etc/ssl/certs} directory, which is where
  4474. most applications and libraries look for certificates by default, points
  4475. to the certificates installed globally.
  4476. Unprivileged users can also install their own certificate package in
  4477. their profile. A number of environment variables need to be defined so
  4478. that applications and libraries know where to find them. Namely, the
  4479. OpenSSL library honors the @code{SSL_CERT_DIR} and @code{SSL_CERT_FILE}
  4480. variables. Some applications add their own environment variables; for
  4481. instance, the Git version control system honors the certificate bundle
  4482. pointed to by the @code{GIT_SSL_CAINFO} environment variable.
  4483. @node Name Service Switch
  4484. @subsection Name Service Switch
  4485. @cindex name service switch
  4486. @cindex NSS
  4487. The @code{(gnu system nss)} module provides bindings to the
  4488. configuration file of libc's @dfn{name service switch} or @dfn{NSS}
  4489. (@pxref{NSS Configuration File,,, libc, The GNU C Library Reference
  4490. Manual}). In a nutshell, the NSS is a mechanism that allows libc to be
  4491. extended with new ``name'' lookup methods for system databases, which
  4492. includes host names, service names, user accounts, and more (@pxref{Name
  4493. Service Switch, System Databases and Name Service Switch,, libc, The GNU
  4494. C Library Reference Manual}).
  4495. The NSS configuration specifies, for each system database, which lookup
  4496. method is to be used, and how the various methods are chained
  4497. together---for instance, under which circumstances NSS should try the
  4498. next method in the list. The NSS configuration is given in the
  4499. @code{name-service-switch} field of @code{operating-system} declarations
  4500. (@pxref{operating-system Reference, @code{name-service-switch}}).
  4501. @cindex nss-mdns
  4502. @cindex .local, host name lookup
  4503. As an example, the declaration below configures the NSS to use the
  4504. @uref{, @code{nss-mdns}
  4505. back-end}, which supports host name lookups over multicast DNS (mDNS)
  4506. for host names ending in @code{.local}:
  4507. @example
  4508. (name-service-switch
  4509. (hosts (list %files ;first, check /etc/hosts
  4510. ;; If the above did not succeed, try
  4511. ;; with 'mdns_minimal'.
  4512. (name-service
  4513. (name "mdns_minimal")
  4514. ;; 'mdns_minimal' is authoritative for
  4515. ;; '.local'. When it returns "not found",
  4516. ;; no need to try the next methods.
  4517. (reaction (lookup-specification
  4518. (not-found => return))))
  4519. ;; Then fall back to DNS.
  4520. (name-service
  4521. (name "dns"))
  4522. ;; Finally, try with the "full" 'mdns'.
  4523. (name-service
  4524. (name "mdns")))))
  4525. @end example
  4526. Don't worry: the @code{%mdns-host-lookup-nss} variable (see below)
  4527. contains this configuration, so you won't have to type it if all you
  4528. want is to have @code{.local} host lookup working.
  4529. Note that, in this case, in addition to setting the
  4530. @code{name-service-switch} of the @code{operating-system} declaration,
  4531. @code{nscd-service} must be told where to find the @code{nss-mdns}
  4532. shared library (@pxref{Base Services, @code{nscd-service}}). Since the
  4533. @code{nscd} service is part of @var{%base-services}, you may want to
  4534. customize it by adding this snippet in the operating system
  4535. configuration file:
  4536. @example
  4537. (use-modules (guix) (gnu))
  4538. (define %my-base-services
  4539. ;; Replace the default nscd service with one that knows
  4540. ;; about nss-mdns.
  4541. (map (lambda (mservice)
  4542. ;; "Bind" the MSERVICE monadic value to inspect it.
  4543. (mlet %store-monad ((service mservice))
  4544. (if (member 'nscd (service-provision service))
  4545. (nscd-service (nscd-configuration)
  4546. #:name-services (list nss-mdns))
  4547. mservice)))
  4548. %base-services))
  4549. @end example
  4550. @noindent
  4551. @dots{} and then refer to @var{%my-base-services} instead of
  4552. @var{%base-services} in the @code{operating-system} declaration.
  4553. Lastly, this relies on the availability of the Avahi service
  4554. (@pxref{Networking Services, @code{avahi-service}}).
  4555. For convenience, the following variables provide typical NSS
  4556. configurations.
  4557. @defvr {Scheme Variable} %default-nss
  4558. This is the default name service switch configuration, a
  4559. @code{name-service-switch} object.
  4560. @end defvr
  4561. @defvr {Scheme Variable} %mdns-host-lookup-nss
  4562. This is the name service switch configuration with support for host name
  4563. lookup over multicast DNS (mDNS) for host names ending in @code{.local}.
  4564. @end defvr
  4565. The reference for name service switch configuration is given below. It
  4566. is a direct mapping of the C library's configuration file format, so
  4567. please refer to the C library manual for more information (@pxref{NSS
  4568. Configuration File,,, libc, The GNU C Library Reference Manual}).
  4569. Compared to libc's NSS configuration file format, it has the advantage
  4570. not only of adding this warm parenthetic feel that we like, but also
  4571. static checks: you'll know about syntax errors and typos as soon as you
  4572. run @command{guix system}.
  4573. @deftp {Data Type} name-service-switch
  4574. This is the data type representation the configuration of libc's name
  4575. service switch (NSS). Each field below represents one of the supported
  4576. system databases.
  4577. @table @code
  4578. @item aliases
  4579. @itemx ethers
  4580. @itemx group
  4581. @itemx gshadow
  4582. @itemx hosts
  4583. @itemx initgroups
  4584. @itemx netgroup
  4585. @itemx networks
  4586. @itemx password
  4587. @itemx public-key
  4588. @itemx rpc
  4589. @itemx services
  4590. @itemx shadow
  4591. The system databases handled by the NSS. Each of these fields must be a
  4592. list of @code{<name-service>} objects (see below.)
  4593. @end table
  4594. @end deftp
  4595. @deftp {Data Type} name-service
  4596. This is the data type representing an actual name service and the
  4597. associated lookup action.
  4598. @table @code
  4599. @item name
  4600. A string denoting the name service (@pxref{Services in the NSS
  4601. configuration,,, libc, The GNU C Library Reference Manual}).
  4602. Note that name services listed here must be visible to nscd. This is
  4603. achieved by passing the @code{#:name-services} argument to
  4604. @code{nscd-service} the list of packages providing the needed name
  4605. services (@pxref{Base Services, @code{nscd-service}}).
  4606. @item reaction
  4607. An action specified using the @code{lookup-specification} macro
  4608. (@pxref{Actions in the NSS configuration,,, libc, The GNU C Library
  4609. Reference Manual}). For example:
  4610. @example
  4611. (lookup-specification (unavailable => continue)
  4612. (success => return))
  4613. @end example
  4614. @end table
  4615. @end deftp
  4616. @node Initial RAM Disk
  4617. @subsection Initial RAM Disk
  4618. @cindex initial RAM disk (initrd)
  4619. @cindex initrd (initial RAM disk)
  4620. For bootstrapping purposes, the Linux-Libre kernel is passed an
  4621. @dfn{initial RAM disk}, or @dfn{initrd}. An initrd contains a temporary
  4622. root file system, as well as an initialization script. The latter is
  4623. responsible for mounting the real root file system, and for loading any
  4624. kernel modules that may be needed to achieve that.
  4625. The @code{initrd} field of an @code{operating-system} declaration allows
  4626. you to specify which initrd you would like to use. The @code{(gnu
  4627. system linux-initrd)} module provides two ways to build an initrd: the
  4628. high-level @code{base-initrd} procedure, and the low-level
  4629. @code{expression->initrd} procedure.
  4630. The @code{base-initrd} procedure is intended to cover most common uses.
  4631. For example, if you want to add a bunch of kernel modules to be loaded
  4632. at boot time, you can define the @code{initrd} field of the operating
  4633. system declaration like this:
  4634. @example
  4635. (initrd (lambda (file-systems . rest)
  4636. ;; Create a standard initrd that has modules "foo.ko"
  4637. ;; and "bar.ko", as well as their dependencies, in
  4638. ;; addition to the modules available by default.
  4639. (apply base-initrd file-systems
  4640. #:extra-modules '("foo" "bar")
  4641. rest)))
  4642. @end example
  4643. The @code{base-initrd} procedure also handles common use cases that
  4644. involves using the system as a QEMU guest, or as a ``live'' system whose
  4645. root file system is volatile.
  4646. @deffn {Monadic Procedure} base-initrd @var{file-systems} @
  4647. [#:qemu-networking? #f] [#:virtio? #f] [#:volatile-root? #f] @
  4648. [#:extra-modules '()] [#:mapped-devices '()]
  4649. Return a monadic derivation that builds a generic initrd. @var{file-systems} is
  4650. a list of file-systems to be mounted by the initrd, possibly in addition to
  4651. the root file system specified on the kernel command line via @code{--root}.
  4652. @var{mapped-devices} is a list of device mappings to realize before
  4653. @var{file-systems} are mounted (@pxref{Mapped Devices}).
  4654. When @var{qemu-networking?} is true, set up networking with the standard QEMU
  4655. parameters. When @var{virtio?} is true, load additional modules so the initrd can
  4656. be used as a QEMU guest with para-virtualized I/O drivers.
  4657. When @var{volatile-root?} is true, the root file system is writable but any changes
  4658. to it are lost.
  4659. The initrd is automatically populated with all the kernel modules necessary
  4660. for @var{file-systems} and for the given options. However, additional kernel
  4661. modules can be listed in @var{extra-modules}. They will be added to the initrd, and
  4662. loaded at boot time in the order in which they appear.
  4663. @end deffn
  4664. Needless to say, the initrds we produce and use embed a
  4665. statically-linked Guile, and the initialization program is a Guile
  4666. program. That gives a lot of flexibility. The
  4667. @code{expression->initrd} procedure builds such an initrd, given the
  4668. program to run in that initrd.
  4669. @deffn {Monadic Procedure} expression->initrd @var{exp} @
  4670. [#:guile %guile-static-stripped] [#:name "guile-initrd"] @
  4671. [#:modules '()]
  4672. Return a derivation that builds a Linux initrd (a gzipped cpio archive)
  4673. containing @var{guile} and that evaluates @var{exp}, a G-expression,
  4674. upon booting. All the derivations referenced by @var{exp} are
  4675. automatically copied to the initrd.
  4676. @var{modules} is a list of Guile module names to be embedded in the
  4677. initrd.
  4678. @end deffn
  4679. @node GRUB Configuration
  4680. @subsection GRUB Configuration
  4681. @cindex GRUB
  4682. @cindex boot loader
  4683. The operating system uses GNU@tie{}GRUB as its boot loader
  4684. (@pxref{Overview, overview of GRUB,, grub, GNU GRUB Manual}). It is
  4685. configured using @code{grub-configuration} declarations. This data type
  4686. is exported by the @code{(gnu system grub)} module, and described below.
  4687. @deftp {Data Type} grub-configuration
  4688. The type of a GRUB configuration declaration.
  4689. @table @asis
  4690. @item @code{device}
  4691. This is a string denoting the boot device. It must be a device name
  4692. understood by the @command{grub-install} command, such as
  4693. @code{/dev/sda} or @code{(hd0)} (@pxref{Invoking grub-install,,, grub,
  4694. GNU GRUB Manual}).
  4695. @item @code{menu-entries} (default: @code{()})
  4696. A possibly empty list of @code{menu-entry} objects (see below), denoting
  4697. entries to appear in the GRUB boot menu, in addition to the current
  4698. system entry and the entry pointing to previous system generations.
  4699. @item @code{default-entry} (default: @code{0})
  4700. The index of the default boot menu entry. Index 0 is for the current
  4701. system's entry.
  4702. @item @code{timeout} (default: @code{5})
  4703. The number of seconds to wait for keyboard input before booting. Set to
  4704. 0 to boot immediately, and to -1 to wait indefinitely.
  4705. @item @code{theme} (default: @var{%default-theme})
  4706. The @code{grub-theme} object describing the theme to use.
  4707. @end table
  4708. @end deftp
  4709. Should you want to list additional boot menu entries @i{via} the
  4710. @code{menu-entries} field above, you will need to create them with the
  4711. @code{menu-entry} form:
  4712. @deftp {Data Type} menu-entry
  4713. The type of an entry in the GRUB boot menu.
  4714. @table @asis
  4715. @item @code{label}
  4716. The label to show in the menu---e.g., @code{"GNU"}.
  4717. @item @code{linux}
  4718. The Linux kernel to boot.
  4719. @item @code{linux-arguments} (default: @code{()})
  4720. The list of extra Linux kernel command-line arguments---e.g.,
  4721. @code{("console=ttyS0")}.
  4722. @item @code{initrd}
  4723. A G-Expression or string denoting the file name of the initial RAM disk
  4724. to use (@pxref{G-Expressions}).
  4725. @end table
  4726. @end deftp
  4727. @c FIXME: Write documentation once it's stable.
  4728. Themes are created using the @code{grub-theme} form, which is not
  4729. documented yet.
  4730. @defvr {Scheme Variable} %default-theme
  4731. This is the default GRUB theme used by the operating system, with a
  4732. fancy background image displaying the GNU and Guix logos.
  4733. @end defvr
  4734. @node Invoking guix system
  4735. @subsection Invoking @code{guix system}
  4736. Once you have written an operating system declaration, as seen in the
  4737. previous section, it can be @dfn{instantiated} using the @command{guix
  4738. system} command. The synopsis is:
  4739. @example
  4740. guix system @var{options}@dots{} @var{action} @var{file}
  4741. @end example
  4742. @var{file} must be the name of a file containing an
  4743. @code{operating-system} declaration. @var{action} specifies how the
  4744. operating system is instantiate. Currently the following values are
  4745. supported:
  4746. @table @code
  4747. @item reconfigure
  4748. Build the operating system described in @var{file}, activate it, and
  4749. switch to it@footnote{This action is usable only on systems already
  4750. running GNU.}.
  4751. This effects all the configuration specified in @var{file}: user
  4752. accounts, system services, global package list, setuid programs, etc.
  4753. It also adds a GRUB menu entry for the new OS configuration, and moves
  4754. entries for older configurations to a submenu---unless
  4755. @option{--no-grub} is passed.
  4756. @c The paragraph below refers to the problem discussed at
  4757. @c <>.
  4758. It is highly recommended to run @command{guix pull} once before you run
  4759. @command{guix system reconfigure} for the first time (@pxref{Invoking
  4760. guix pull}). Failing to do that you would see an older version of Guix
  4761. once @command{reconfigure} has completed.
  4762. @item build
  4763. Build the operating system's derivation, which includes all the
  4764. configuration files and programs needed to boot and run the system.
  4765. This action does not actually install anything.
  4766. @item init
  4767. Populate the given directory with all the files necessary to run the
  4768. operating system specified in @var{file}. This is useful for first-time
  4769. installations of GuixSD. For instance:
  4770. @example
  4771. guix system init my-os-config.scm /mnt
  4772. @end example
  4773. copies to @file{/mnt} all the store items required by the configuration
  4774. specified in @file{my-os-config.scm}. This includes configuration
  4775. files, packages, and so on. It also creates other essential files
  4776. needed for the system to operate correctly---e.g., the @file{/etc},
  4777. @file{/var}, and @file{/run} directories, and the @file{/bin/sh} file.
  4778. This command also installs GRUB on the device specified in
  4779. @file{my-os-config}, unless the @option{--no-grub} option was passed.
  4780. @item vm
  4781. @cindex virtual machine
  4782. @cindex VM
  4783. Build a virtual machine that contain the operating system declared in
  4784. @var{file}, and return a script to run that virtual machine (VM).
  4785. Arguments given to the script are passed as is to QEMU.
  4786. The VM shares its store with the host system.
  4787. Additional file systems can be shared between the host and the VM using
  4788. the @code{--share} and @code{--expose} command-line options: the former
  4789. specifies a directory to be shared with write access, while the latter
  4790. provides read-only access to the shared directory.
  4791. The example below creates a VM in which the user's home directory is
  4792. accessible read-only, and where the @file{/exchange} directory is a
  4793. read-write mapping of the host's @file{$HOME/tmp}:
  4794. @example
  4795. guix system vm my-config.scm \
  4796. --expose=$HOME --share=$HOME/tmp=/exchange
  4797. @end example
  4798. On GNU/Linux, the default is to boot directly to the kernel; this has
  4799. the advantage of requiring only a very tiny root disk image since the
  4800. host's store can then be mounted.
  4801. The @code{--full-boot} option forces a complete boot sequence, starting
  4802. with the bootloader. This requires more disk space since a root image
  4803. containing at least the kernel, initrd, and bootloader data files must
  4804. be created. The @code{--image-size} option can be used to specify the
  4805. image's size.
  4806. @item vm-image
  4807. @itemx disk-image
  4808. Return a virtual machine or disk image of the operating system declared
  4809. in @var{file} that stands alone. Use the @option{--image-size} option
  4810. to specify the size of the image.
  4811. When using @code{vm-image}, the returned image is in qcow2 format, which
  4812. the QEMU emulator can efficiently use.
  4813. When using @code{disk-image}, a raw disk image is produced; it can be
  4814. copied as is to a USB stick, for instance. Assuming @code{/dev/sdc} is
  4815. the device corresponding to a USB stick, one can copy the image on it
  4816. using the following command:
  4817. @example
  4818. # dd if=$(guix system disk-image my-os.scm) of=/dev/sdc
  4819. @end example
  4820. @end table
  4821. @var{options} can contain any of the common build options provided by
  4822. @command{guix build} (@pxref{Invoking guix build}). In addition,
  4823. @var{options} can contain one of the following:
  4824. @table @option
  4825. @item --system=@var{system}
  4826. @itemx -s @var{system}
  4827. Attempt to build for @var{system} instead of the host's system type.
  4828. This works as per @command{guix build} (@pxref{Invoking guix build}).
  4829. @item --image-size=@var{size}
  4830. For the @code{vm-image} and @code{disk-image} actions, create an image
  4831. of the given @var{size}. @var{size} may be a number of bytes, or it may
  4832. include a unit as a suffix (@pxref{Block size, size specifications,,
  4833. coreutils, GNU Coreutils}).
  4834. @item --on-error=@var{strategy}
  4835. Apply @var{strategy} when an error occurs when reading @var{file}.
  4836. @var{strategy} may be one of the following:
  4837. @table @code
  4838. @item nothing-special
  4839. Report the error concisely and exit. This is the default strategy.
  4840. @item backtrace
  4841. Likewise, but also display a backtrace.
  4842. @item debug
  4843. Report the error and enter Guile's debugger. From there, you can run
  4844. commands such as @code{,bt} to get a backtrace, @code{,locals} to
  4845. display local variable values, and more generally inspect the program's
  4846. state. @xref{Debug Commands,,, guile, GNU Guile Reference Manual}, for
  4847. a list of available debugging commands.
  4848. @end table
  4849. @end table
  4850. Note that all the actions above, except @code{build} and @code{init},
  4851. rely on KVM support in the Linux-Libre kernel. Specifically, the
  4852. machine should have hardware virtualization support, the corresponding
  4853. KVM kernel module should be loaded, and the @file{/dev/kvm} device node
  4854. must exist and be readable and writable by the user and by the daemon's
  4855. build users.
  4856. @node Defining Services
  4857. @subsection Defining Services
  4858. The @code{(gnu services @dots{})} modules define several procedures that allow
  4859. users to declare the operating system's services (@pxref{Using the
  4860. Configuration System}). These procedures are @emph{monadic
  4861. procedures}---i.e., procedures that return a monadic value in the store
  4862. monad (@pxref{The Store Monad}). For examples of such procedures,
  4863. @xref{Services}.
  4864. @cindex service definition
  4865. The monadic value returned by those procedures is a @dfn{service
  4866. definition}---a structure as returned by the @code{service} form.
  4867. Service definitions specifies the inputs the service depends on, and an
  4868. expression to start and stop the service. Behind the scenes, service
  4869. definitions are ``translated'' into the form suitable for the
  4870. configuration file of dmd, the init system (@pxref{Services,,, dmd, GNU
  4871. dmd Manual}).
  4872. As an example, here is what the @code{nscd-service} procedure looks
  4873. like:
  4874. @lisp
  4875. (define (nscd-service)
  4876. (with-monad %store-monad
  4877. (return (service
  4878. (documentation "Run libc's name service cache daemon.")
  4879. (provision '(nscd))
  4880. (activate #~(begin
  4881. (use-modules (guix build utils))
  4882. (mkdir-p "/var/run/nscd")))
  4883. (start #~(make-forkexec-constructor
  4884. (string-append #$glibc "/sbin/nscd")
  4885. "-f" "/dev/null" "--foreground"))
  4886. (stop #~(make-kill-destructor))
  4887. (respawn? #f)))))
  4888. @end lisp
  4889. @noindent
  4890. The @code{activate}, @code{start}, and @code{stop} fields are G-expressions
  4891. (@pxref{G-Expressions}). The @code{activate} field contains a script to
  4892. run at ``activation'' time; it makes sure that the @file{/var/run/nscd}
  4893. directory exists before @command{nscd} is started.
  4894. The @code{start} and @code{stop} fields refer to dmd's facilities to
  4895. start and stop processes (@pxref{Service De- and Constructors,,, dmd,
  4896. GNU dmd Manual}). The @code{provision} field specifies the name under
  4897. which this service is known to dmd, and @code{documentation} specifies
  4898. on-line documentation. Thus, the commands @command{deco start ncsd},
  4899. @command{deco stop nscd}, and @command{deco doc nscd} will do what you
  4900. would expect (@pxref{Invoking deco,,, dmd, GNU dmd Manual}).
  4901. @node Installing Debugging Files
  4902. @section Installing Debugging Files
  4903. @cindex debugging files
  4904. Program binaries, as produced by the GCC compilers for instance, are
  4905. typically written in the ELF format, with a section containing
  4906. @dfn{debugging information}. Debugging information is what allows the
  4907. debugger, GDB, to map binary code to source code; it is required to
  4908. debug a compiled program in good conditions.
  4909. The problem with debugging information is that is takes up a fair amount
  4910. of disk space. For example, debugging information for the GNU C Library
  4911. weighs in at more than 60 MiB. Thus, as a user, keeping all the
  4912. debugging info of all the installed programs is usually not an option.
  4913. Yet, space savings should not come at the cost of an impediment to
  4914. debugging---especially in the GNU system, which should make it easier
  4915. for users to exert their computing freedom (@pxref{GNU Distribution}).
  4916. Thankfully, the GNU Binary Utilities (Binutils) and GDB provide a
  4917. mechanism that allows users to get the best of both worlds: debugging
  4918. information can be stripped from the binaries and stored in separate
  4919. files. GDB is then able to load debugging information from those files,
  4920. when they are available (@pxref{Separate Debug Files,,, gdb, Debugging
  4921. with GDB}).
  4922. The GNU distribution takes advantage of this by storing debugging
  4923. information in the @code{lib/debug} sub-directory of a separate package
  4924. output unimaginatively called @code{debug} (@pxref{Packages with
  4925. Multiple Outputs}). Users can choose to install the @code{debug} output
  4926. of a package when they need it. For instance, the following command
  4927. installs the debugging information for the GNU C Library and for GNU
  4928. Guile:
  4929. @example
  4930. guix package -i glibc:debug guile:debug
  4931. @end example
  4932. GDB must then be told to look for debug files in the user's profile, by
  4933. setting the @code{debug-file-directory} variable (consider setting it
  4934. from the @file{~/.gdbinit} file, @pxref{Startup,,, gdb, Debugging with
  4935. GDB}):
  4936. @example
  4937. (gdb) set debug-file-directory ~/.guix-profile/lib/debug
  4938. @end example
  4939. From there on, GDB will pick up debugging information from the
  4940. @code{.debug} files under @file{~/.guix-profile/lib/debug}.
  4941. In addition, you will most likely want GDB to be able to show the source
  4942. code being debugged. To do that, you will have to unpack the source
  4943. code of the package of interest (obtained with @code{guix build
  4944. --source}, @pxref{Invoking guix build}), and to point GDB to that source
  4945. directory using the @code{directory} command (@pxref{Source Path,
  4946. @code{directory},, gdb, Debugging with GDB}).
  4947. @c XXX: keep me up-to-date
  4948. The @code{debug} output mechanism in Guix is implemented by the
  4949. @code{gnu-build-system} (@pxref{Build Systems}). Currently, it is
  4950. opt-in---debugging information is available only for those packages
  4951. whose definition explicitly declares a @code{debug} output. This may be
  4952. changed to opt-out in the future, if our build farm servers can handle
  4953. the load. To check whether a package has a @code{debug} output, use
  4954. @command{guix package --list-available} (@pxref{Invoking guix package}).
  4955. @node Security Updates
  4956. @section Security Updates
  4957. @quotation Note
  4958. As of version @value{VERSION}, the feature described in this section is
  4959. experimental.
  4960. @end quotation
  4961. @cindex security updates
  4962. Occasionally, important security vulnerabilities are discovered in core
  4963. software packages and must be patched. Guix follows a functional
  4964. package management discipline (@pxref{Introduction}), which implies
  4965. that, when a package is changed, @emph{every package that depends on it}
  4966. must be rebuilt. This can significantly slow down the deployment of
  4967. fixes in core packages such as libc or Bash, since basically the whole
  4968. distribution would need to be rebuilt. Using pre-built binaries helps
  4969. (@pxref{Substitutes}), but deployment may still take more time than
  4970. desired.
  4971. @cindex grafts
  4972. To address that, Guix implements @dfn{grafts}, a mechanism that allows
  4973. for fast deployment of critical updates without the costs associated
  4974. with a whole-distribution rebuild. The idea is to rebuild only the
  4975. package that needs to be patched, and then to ``graft'' it onto packages
  4976. explicitly installed by the user and that were previously referring to
  4977. the original package. The cost of grafting is typically very low, and
  4978. order of magnitudes lower than a full rebuild of the dependency chain.
  4979. @cindex replacements of packages, for grafts
  4980. For instance, suppose a security update needs to be applied to Bash.
  4981. Guix developers will provide a package definition for the ``fixed''
  4982. Bash, say @var{bash-fixed}, in the usual way (@pxref{Defining
  4983. Packages}). Then, the original package definition is augmented with a
  4984. @code{replacement} field pointing to the package containing the bug fix:
  4985. @example
  4986. (define bash
  4987. (package
  4988. (name "bash")
  4989. ;; @dots{}
  4990. (replacement bash-fixed)))
  4991. @end example
  4992. From there on, any package depending directly or indirectly on Bash that
  4993. is installed will automatically be ``rewritten'' to refer to
  4994. @var{bash-fixed} instead of @var{bash}. This grafting process takes
  4995. time proportional to the size of the package, but expect less than a
  4996. minute for an ``average'' package on a recent machine.
  4997. Currently, the graft and the package it replaces (@var{bash-fixed} and
  4998. @var{bash} in the example above) must have the exact same @code{name}
  4999. and @code{version} fields. This restriction mostly comes from the fact
  5000. that grafting works by patching files, including binary files, directly.
  5001. Other restrictions may apply: for instance, when adding a graft to a
  5002. package providing a shared library, the original shared library and its
  5003. replacement must have the same @code{SONAME} and be binary-compatible.
  5004. @node Package Modules
  5005. @section Package Modules
  5006. From a programming viewpoint, the package definitions of the
  5007. GNU distribution are provided by Guile modules in the @code{(gnu packages
  5008. @dots{})} name space@footnote{Note that packages under the @code{(gnu
  5009. packages @dots{})} module name space are not necessarily ``GNU
  5010. packages''. This module naming scheme follows the usual Guile module
  5011. naming convention: @code{gnu} means that these modules are distributed
  5012. as part of the GNU system, and @code{packages} identifies modules that
  5013. define packages.} (@pxref{Modules, Guile modules,, guile, GNU Guile
  5014. Reference Manual}). For instance, the @code{(gnu packages emacs)}
  5015. module exports a variable named @code{emacs}, which is bound to a
  5016. @code{<package>} object (@pxref{Defining Packages}).
  5017. The @code{(gnu packages @dots{})} module name space is
  5018. automatically scanned for packages by the command-line tools. For
  5019. instance, when running @code{guix package -i emacs}, all the @code{(gnu
  5020. packages @dots{})} modules are scanned until one that exports a package
  5021. object whose name is @code{emacs} is found. This package search
  5022. facility is implemented in the @code{(gnu packages)} module.
  5023. @cindex customization, of packages
  5024. @cindex package module search path
  5025. Users can store package definitions in modules with different
  5026. names---e.g., @code{(my-packages emacs)}@footnote{Note that the file
  5027. name and module name must match. For instance, the @code{(my-packages
  5028. emacs)} module must be stored in a @file{my-packages/emacs.scm} file
  5029. relative to the load path specified with @option{--load-path} or
  5030. @code{GUIX_PACKAGE_PATH}. @xref{Modules and the File System,,,
  5031. guile, GNU Guile Reference Manual}, for details.}. These package definitions
  5032. will not be visible by default. Thus, users can invoke commands such as
  5033. @command{guix package} and @command{guix build} have to be used with the
  5034. @code{-e} option so that they know where to find the package. Better
  5035. yet, they can use the
  5036. @code{-L} option of these commands to make those modules visible
  5037. (@pxref{Invoking guix build, @code{--load-path}}), or define the
  5038. @code{GUIX_PACKAGE_PATH} environment variable. This environment
  5039. variable makes it easy to extend or customize the distribution and is
  5040. honored by all the user interfaces.
  5041. @defvr {Environment Variable} GUIX_PACKAGE_PATH
  5042. This is a colon-separated list of directories to search for package
  5043. modules. Directories listed in this variable take precedence over the
  5044. distribution's own modules.
  5045. @end defvr
  5046. The distribution is fully @dfn{bootstrapped} and @dfn{self-contained}:
  5047. each package is built based solely on other packages in the
  5048. distribution. The root of this dependency graph is a small set of
  5049. @dfn{bootstrap binaries}, provided by the @code{(gnu packages
  5050. bootstrap)} module. For more information on bootstrapping,
  5051. @pxref{Bootstrapping}.
  5052. @node Packaging Guidelines
  5053. @section Packaging Guidelines
  5054. The GNU distribution is nascent and may well lack some of your favorite
  5055. packages. This section describes how you can help make the distribution
  5056. grow. @xref{Contributing}, for additional information on how you can
  5057. help.
  5058. Free software packages are usually distributed in the form of
  5059. @dfn{source code tarballs}---typically @file{tar.gz} files that contain
  5060. all the source files. Adding a package to the distribution means
  5061. essentially two things: adding a @dfn{recipe} that describes how to
  5062. build the package, including a list of other packages required to build
  5063. it, and adding @dfn{package meta-data} along with that recipe, such as a
  5064. description and licensing information.
  5065. In Guix all this information is embodied in @dfn{package definitions}.
  5066. Package definitions provide a high-level view of the package. They are
  5067. written using the syntax of the Scheme programming language; in fact,
  5068. for each package we define a variable bound to the package definition,
  5069. and export that variable from a module (@pxref{Package Modules}).
  5070. However, in-depth Scheme knowledge is @emph{not} a prerequisite for
  5071. creating packages. For more information on package definitions,
  5072. @pxref{Defining Packages}.
  5073. Once a package definition is in place, stored in a file in the Guix
  5074. source tree, it can be tested using the @command{guix build} command
  5075. (@pxref{Invoking guix build}). For example, assuming the new package is
  5076. called @code{gnew}, you may run this command from the Guix build tree
  5077. (@pxref{Running Guix Before It Is Installed}):
  5078. @example
  5079. ./pre-inst-env guix build gnew --keep-failed
  5080. @end example
  5081. Using @code{--keep-failed} makes it easier to debug build failures since
  5082. it provides access to the failed build tree. Another useful
  5083. command-line option when debugging is @code{--log-file}, to access the
  5084. build log.
  5085. If the package is unknown to the @command{guix} command, it may be that
  5086. the source file contains a syntax error, or lacks a @code{define-public}
  5087. clause to export the package variable. To figure it out, you may load
  5088. the module from Guile to get more information about the actual error:
  5089. @example
  5090. ./pre-inst-env guile -c '(use-modules (gnu packages gnew))'
  5091. @end example
  5092. Once your package builds correctly, please send us a patch
  5093. (@pxref{Contributing}). Well, if you need help, we will be happy to
  5094. help you too. Once the patch is committed in the Guix repository, the
  5095. new package automatically gets built on the supported platforms by
  5096. @url{, our continuous integration
  5097. system}.
  5098. @cindex substituter
  5099. Users can obtain the new package definition simply by running
  5100. @command{guix pull} (@pxref{Invoking guix pull}). When
  5101. @code{} is done building the package, installing the
  5102. package automatically downloads binaries from there
  5103. (@pxref{Substitutes}). The only place where human intervention is
  5104. needed is to review and apply the patch.
  5105. @menu
  5106. * Software Freedom:: What may go into the distribution.
  5107. * Package Naming:: What's in a name?
  5108. * Version Numbers:: When the name is not enough.
  5109. * Python Modules:: Taming the snake.
  5110. * Perl Modules:: Little pearls.
  5111. * Fonts:: Fond of fonts.
  5112. @end menu
  5113. @node Software Freedom
  5114. @subsection Software Freedom
  5115. @c Adapted from
  5116. The GNU operating system has been developed so that users can have
  5117. freedom in their computing. GNU is @dfn{free software}, meaning that
  5118. users have the @url{,four
  5119. essential freedoms}: to run the program, to study and change the program
  5120. in source code form, to redistribute exact copies, and to distribute
  5121. modified versions. Packages found in the GNU distribution provide only
  5122. software that conveys these four freedoms.
  5123. In addition, the GNU distribution follow the
  5124. @url{,free
  5125. software distribution guidelines}. Among other things, these guidelines
  5126. reject non-free firmware, recommendations of non-free software, and
  5127. discuss ways to deal with trademarks and patents.
  5128. Some packages contain a small and optional subset that violates the
  5129. above guidelines, for instance because this subset is itself non-free
  5130. code. When that happens, the offending items are removed with
  5131. appropriate patches or code snippets in the package definition's
  5132. @code{origin} form (@pxref{Defining Packages}). That way, @code{guix
  5133. build --source} returns the ``freed'' source rather than the unmodified
  5134. upstream source.
  5135. @node Package Naming
  5136. @subsection Package Naming
  5137. A package has actually two names associated with it:
  5138. First, there is the name of the @emph{Scheme variable}, the one following
  5139. @code{define-public}. By this name, the package can be made known in the
  5140. Scheme code, for instance as input to another package. Second, there is
  5141. the string in the @code{name} field of a package definition. This name
  5142. is used by package management commands such as
  5143. @command{guix package} and @command{guix build}.
  5144. Both are usually the same and correspond to the lowercase conversion of
  5145. the project name chosen upstream, with underscores replaced with
  5146. hyphens. For instance, GNUnet is available as @code{gnunet}, and
  5147. SDL_net as @code{sdl-net}.
  5148. We do not add @code{lib} prefixes for library packages, unless these are
  5149. already part of the official project name. But @pxref{Python
  5150. Modules} and @ref{Perl Modules} for special rules concerning modules for
  5151. the Python and Perl languages.
  5152. Font package names are handled differently, @pxref{Fonts}.
  5153. @node Version Numbers
  5154. @subsection Version Numbers
  5155. We usually package only the latest version of a given free software
  5156. project. But sometimes, for instance for incompatible library versions,
  5157. two (or more) versions of the same package are needed. These require
  5158. different Scheme variable names. We use the name as defined
  5159. in @ref{Package Naming}
  5160. for the most recent version; previous versions use the same name, suffixed
  5161. by @code{-} and the smallest prefix of the version number that may
  5162. distinguish the two versions.
  5163. The name inside the package definition is the same for all versions of a
  5164. package and does not contain any version number.
  5165. For instance, the versions 2.24.20 and 3.9.12 of GTK+ may be packaged as follows:
  5166. @example
  5167. (define-public gtk+
  5168. (package
  5169. (name "gtk+")
  5170. (version "3.9.12")
  5171. ...))
  5172. (define-public gtk+-2
  5173. (package
  5174. (name "gtk+")
  5175. (version "2.24.20")
  5176. ...))
  5177. @end example
  5178. If we also wanted GTK+ 3.8.2, this would be packaged as
  5179. @example
  5180. (define-public gtk+-3.8
  5181. (package
  5182. (name "gtk+")
  5183. (version "3.8.2")
  5184. ...))
  5185. @end example
  5186. @node Python Modules
  5187. @subsection Python Modules
  5188. We currently package Python 2 and Python 3, under the Scheme variable names
  5189. @code{python-2} and @code{python} as explained in @ref{Version Numbers}.
  5190. To avoid confusion and naming clashes with other programming languages, it
  5191. seems desirable that the name of a package for a Python module contains
  5192. the word @code{python}.
  5193. Some modules are compatible with only one version of Python, others with both.
  5194. If the package Foo compiles only with Python 3, we name it
  5195. @code{python-foo}; if it compiles only with Python 2, we name it
  5196. @code{python2-foo}. If it is compatible with both versions, we create two
  5197. packages with the corresponding names.
  5198. If a project already contains the word @code{python}, we drop this;
  5199. for instance, the module python-dateutil is packaged under the names
  5200. @code{python-dateutil} and @code{python2-dateutil}.
  5201. @node Perl Modules
  5202. @subsection Perl Modules
  5203. Perl programs standing for themselves are named as any other package,
  5204. using the lowercase upstream name.
  5205. For Perl packages containing a single class, we use the lowercase class name,
  5206. replace all occurrences of @code{::} by dashes and prepend the prefix
  5207. @code{perl-}.
  5208. So the class @code{XML::Parser} becomes @code{perl-xml-parser}.
  5209. Modules containing several classes keep their lowercase upstream name and
  5210. are also prepended by @code{perl-}. Such modules tend to have the word
  5211. @code{perl} somewhere in their name, which gets dropped in favor of the
  5212. prefix. For instance, @code{libwww-perl} becomes @code{perl-libwww}.
  5213. @node Fonts
  5214. @subsection Fonts
  5215. For fonts that are in general not installed by a user for typesetting
  5216. purposes, or that are distributed as part of a larger software package,
  5217. we rely on the general packaging rules for software; for instance, this
  5218. applies to the fonts delivered as part of the X.Org system or fonts that
  5219. are part of TeX Live.
  5220. To make it easier for a user to search for fonts, names for other packages
  5221. containing only fonts are constructed as follows, independently of the
  5222. upstream package name.
  5223. The name of a package containing only one font family starts with
  5224. @code{font-}; it is followed by the foundry name and a dash @code{-}
  5225. if the foundry is known, and the font family name, in which spaces are
  5226. replaced by dashes (and as usual, all upper case letters are transformed
  5227. to lower case).
  5228. For example, the Gentium font family by SIL is packaged under the name
  5229. @code{font-sil-gentium}.
  5230. For a package containing several font families, the name of the collection
  5231. is used in the place of the font family name.
  5232. For instance, the Liberation fonts consist of three families,
  5233. Liberation Sans, Liberation Serif and Liberation Mono.
  5234. These could be packaged separately under the names
  5235. @code{font-liberation-sans} and so on; but as they are distributed together
  5236. under a common name, we prefer to package them together as
  5237. @code{font-liberation}.
  5238. In the case where several formats of the same font family or font collection
  5239. are packaged separately, a short form of the format, prepended by a dash,
  5240. is added to the package name. We use @code{-ttf} for TrueType fonts,
  5241. @code{-otf} for OpenType fonts and @code{-type1} for PostScript Type 1
  5242. fonts.
  5243. @node Bootstrapping
  5244. @section Bootstrapping
  5245. @c Adapted from the ELS 2013 paper.
  5246. @cindex bootstrapping
  5247. Bootstrapping in our context refers to how the distribution gets built
  5248. ``from nothing''. Remember that the build environment of a derivation
  5249. contains nothing but its declared inputs (@pxref{Introduction}). So
  5250. there's an obvious chicken-and-egg problem: how does the first package
  5251. get built? How does the first compiler get compiled? Note that this is
  5252. a question of interest only to the curious hacker, not to the regular
  5253. user, so you can shamelessly skip this section if you consider yourself
  5254. a ``regular user''.
  5255. @cindex bootstrap binaries
  5256. The GNU system is primarily made of C code, with libc at its core. The
  5257. GNU build system itself assumes the availability of a Bourne shell and
  5258. command-line tools provided by GNU Coreutils, Awk, Findutils, `sed', and
  5259. `grep'. Furthermore, build programs---programs that run
  5260. @code{./configure}, @code{make}, etc.---are written in Guile Scheme
  5261. (@pxref{Derivations}). Consequently, to be able to build anything at
  5262. all, from scratch, Guix relies on pre-built binaries of Guile, GCC,
  5263. Binutils, libc, and the other packages mentioned above---the
  5264. @dfn{bootstrap binaries}.
  5265. These bootstrap binaries are ``taken for granted'', though we can also
  5266. re-create them if needed (more on that later).
  5267. @unnumberedsubsec Preparing to Use the Bootstrap Binaries
  5268. @c As of Emacs 24.3, Info-mode displays the image, but since it's a
  5269. @c large image, it's hard to scroll. Oh well.
  5270. @image{images/bootstrap-graph,6in,,Dependency graph of the early bootstrap derivations}
  5271. The figure above shows the very beginning of the dependency graph of the
  5272. distribution, corresponding to the package definitions of the @code{(gnu
  5273. packages bootstrap)} module. At this level of detail, things are
  5274. slightly complex. First, Guile itself consists of an ELF executable,
  5275. along with many source and compiled Scheme files that are dynamically
  5276. loaded when it runs. This gets stored in the @file{guile-2.0.7.tar.xz}
  5277. tarball shown in this graph. This tarball is part of Guix's ``source''
  5278. distribution, and gets inserted into the store with @code{add-to-store}
  5279. (@pxref{The Store}).
  5280. But how do we write a derivation that unpacks this tarball and adds it
  5281. to the store? To solve this problem, the @code{guile-bootstrap-2.0.drv}
  5282. derivation---the first one that gets built---uses @code{bash} as its
  5283. builder, which runs @code{}, which in turn calls
  5284. @code{tar} to unpack the tarball. Thus, @file{bash}, @file{tar},
  5285. @file{xz}, and @file{mkdir} are statically-linked binaries, also part of
  5286. the Guix source distribution, whose sole purpose is to allow the Guile
  5287. tarball to be unpacked.
  5288. Once @code{guile-bootstrap-2.0.drv} is built, we have a functioning
  5289. Guile that can be used to run subsequent build programs. Its first task
  5290. is to download tarballs containing the other pre-built binaries---this
  5291. is what the @code{.tar.xz.drv} derivations do. Guix modules such as
  5292. @code{ftp-client.scm} are used for this purpose. The
  5293. @code{module-import.drv} derivations import those modules in a directory
  5294. in the store, using the original layout. The
  5295. @code{module-import-compiled.drv} derivations compile those modules, and
  5296. write them in an output directory with the right layout. This
  5297. corresponds to the @code{#:modules} argument of
  5298. @code{build-expression->derivation} (@pxref{Derivations}).
  5299. Finally, the various tarballs are unpacked by the
  5300. derivations @code{gcc-bootstrap-0.drv}, @code{glibc-bootstrap-0.drv},
  5301. etc., at which point we have a working C tool chain.
  5302. @unnumberedsubsec Building the Build Tools
  5303. @c TODO: Add a package-level dependency graph generated from (gnu
  5304. @c packages base).
  5305. Bootstrapping is complete when we have a full tool chain that does not
  5306. depend on the pre-built bootstrap tools discussed above. This
  5307. no-dependency requirement is verified by checking whether the files of
  5308. the final tool chain contain references to the @file{/gnu/store}
  5309. directories of the bootstrap inputs. The process that leads to this
  5310. ``final'' tool chain is described by the package definitions found in
  5311. the @code{(gnu packages commencement)} module.
  5312. @c See <>.
  5313. The first tool that gets built with the bootstrap binaries is
  5314. GNU Make, which is a prerequisite for all the following packages.
  5315. From there Findutils and Diffutils get built.
  5316. Then come the first-stage Binutils and GCC, built as pseudo cross
  5317. tools---i.e., with @code{--target} equal to @code{--host}. They are
  5318. used to build libc. Thanks to this cross-build trick, this libc is
  5319. guaranteed not to hold any reference to the initial tool chain.
  5320. From there the final Binutils and GCC are built. GCC uses @code{ld}
  5321. from the final Binutils, and links programs against the just-built libc.
  5322. This tool chain is used to build the other packages used by Guix and by
  5323. the GNU Build System: Guile, Bash, Coreutils, etc.
  5324. And voilà! At this point we have the complete set of build tools that
  5325. the GNU Build System expects. These are in the @code{%final-inputs}
  5326. variable of the @code{(gnu packages commencement)} module, and are
  5327. implicitly used by any package that uses @code{gnu-build-system}
  5328. (@pxref{Build Systems, @code{gnu-build-system}}).
  5329. @unnumberedsubsec Building the Bootstrap Binaries
  5330. Because the final tool chain does not depend on the bootstrap binaries,
  5331. those rarely need to be updated. Nevertheless, it is useful to have an
  5332. automated way to produce them, should an update occur, and this is what
  5333. the @code{(gnu packages make-bootstrap)} module provides.
  5334. The following command builds the tarballs containing the bootstrap
  5335. binaries (Guile, Binutils, GCC, libc, and a tarball containing a mixture
  5336. of Coreutils and other basic command-line tools):
  5337. @example
  5338. guix build bootstrap-tarballs
  5339. @end example
  5340. The generated tarballs are those that should be referred to in the
  5341. @code{(gnu packages bootstrap)} module mentioned at the beginning of
  5342. this section.
  5343. Still here? Then perhaps by now you've started to wonder: when do we
  5344. reach a fixed point? That is an interesting question! The answer is
  5345. unknown, but if you would like to investigate further (and have
  5346. significant computational and storage resources to do so), then let us
  5347. know.
  5348. @node Porting
  5349. @section Porting to a New Platform
  5350. As discussed above, the GNU distribution is self-contained, and
  5351. self-containment is achieved by relying on pre-built ``bootstrap
  5352. binaries'' (@pxref{Bootstrapping}). These binaries are specific to an
  5353. operating system kernel, CPU architecture, and application binary
  5354. interface (ABI). Thus, to port the distribution to a platform that is
  5355. not yet supported, one must build those bootstrap binaries, and update
  5356. the @code{(gnu packages bootstrap)} module to use them on that platform.
  5357. Fortunately, Guix can @emph{cross compile} those bootstrap binaries.
  5358. When everything goes well, and assuming the GNU tool chain supports the
  5359. target platform, this can be as simple as running a command like this
  5360. one:
  5361. @example
  5362. guix build --target=armv5tel-linux-gnueabi bootstrap-tarballs
  5363. @end example
  5364. For this to work, the @code{glibc-dynamic-linker} procedure in
  5365. @code{(gnu packages bootstrap)} must be augmented to return the right
  5366. file name for libc's dynamic linker on that platform; likewise,
  5367. @code{system->linux-architecture} in @code{(gnu packages linux)} must be
  5368. taught about the new platform.
  5369. Once these are built, the @code{(gnu packages bootstrap)} module needs
  5370. to be updated to refer to these binaries on the target platform. That
  5371. is, the hashes and URLs of the bootstrap tarballs for the new platform
  5372. must be added alongside those of the currently supported platforms. The
  5373. bootstrap Guile tarball is treated specially: it is expected to be
  5374. available locally, and @file{} has rules do download it for
  5375. the supported architectures; a rule for the new platform must be added
  5376. as well.
  5377. In practice, there may be some complications. First, it may be that the
  5378. extended GNU triplet that specifies an ABI (like the @code{eabi} suffix
  5379. above) is not recognized by all the GNU tools. Typically, glibc
  5380. recognizes some of these, whereas GCC uses an extra @code{--with-abi}
  5381. configure flag (see @code{gcc.scm} for examples of how to handle this).
  5382. Second, some of the required packages could fail to build for that
  5383. platform. Lastly, the generated binaries could be broken for some
  5384. reason.
  5385. @c *********************************************************************
  5386. @include contributing.texi
  5387. @c *********************************************************************
  5388. @node Acknowledgments
  5389. @chapter Acknowledgments
  5390. Guix is based on the Nix package manager, which was designed and
  5391. implemented by Eelco Dolstra, with contributions from other people (see
  5392. the @file{nix/AUTHORS} file in Guix.) Nix pioneered functional package
  5393. management, and promoted unprecedented features, such as transactional
  5394. package upgrades and rollbacks, per-user profiles, and referentially
  5395. transparent build processes. Without this work, Guix would not exist.
  5396. The Nix-based software distributions, Nixpkgs and NixOS, have also been
  5397. an inspiration for Guix.
  5398. GNU@tie{}Guix itself is a collective work with contributions from a
  5399. number of people. See the @file{AUTHORS} file in Guix for more
  5400. information on these fine people. The @file{THANKS} file lists people
  5401. who have helped by reporting bugs, taking care of the infrastructure,
  5402. providing artwork and themes, making suggestions, and more---thank you!
  5403. @c *********************************************************************
  5404. @node GNU Free Documentation License
  5405. @appendix GNU Free Documentation License
  5406. @include fdl-1.3.texi
  5407. @c *********************************************************************
  5408. @node Concept Index
  5409. @unnumbered Concept Index
  5410. @printindex cp
  5411. @node Programming Index
  5412. @unnumbered Programming Index
  5413. @syncodeindex tp fn
  5414. @syncodeindex vr fn
  5415. @printindex fn
  5416. @bye
  5417. @c Local Variables:
  5418. @c ispell-local-dictionary: "american";
  5419. @c End: