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\input texinfo
@c -*-texinfo-*-
@c %**start of header
@setfilename guix.info
@documentencoding UTF-8
@settitle GNU Guix Reference Manual
@c %**end of header
@include version.texi
@copying
Copyright @copyright{} 2012, 2013, 2014, 2015 Ludovic Courtès@*
Copyright @copyright{} 2013, 2014 Andreas Enge@*
Copyright @copyright{} 2013 Nikita Karetnikov
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
any later version published by the Free Software Foundation; with no
Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A
copy of the license is included in the section entitled ``GNU Free
Documentation License''.
@end copying
@dircategory Package management
@direntry
* guix: (guix). Guix, the functional package manager.
* guix package: (guix)Invoking guix package
Managing packages with Guix.
* guix build: (guix)Invoking guix build
Building packages with Guix.
* guix system: (guix)Invoking guix system
Managing the operating system configuration.
@end direntry
@dircategory Software development
@direntry
* guix environment: (guix)Invoking guix environment
Building development environments with Guix.
@end direntry
@titlepage
@title GNU Guix Reference Manual
@subtitle Using the GNU Guix Functional Package Manager
@author Ludovic Courtès
@author Andreas Enge
@author Nikita Karetnikov
@page
@vskip 0pt plus 1filll
Edition @value{EDITION} @*
@value{UPDATED} @*
@insertcopying
@end titlepage
@contents
@c *********************************************************************
@node Top
@top GNU Guix
This document describes GNU Guix version @value{VERSION}, a functional
package management tool written for the GNU system.
@menu
* Introduction:: What is Guix about?
* Installation:: Installing Guix.
* Package Management:: Package installation, upgrade, etc.
* Programming Interface:: Using Guix in Scheme.
* Utilities:: Package management commands.
* GNU Distribution:: Software for your friendly GNU system.
* Contributing:: Your help needed!
* Acknowledgments:: Thanks!
* GNU Free Documentation License:: The license of this manual.
* Concept Index:: Concepts.
* Programming Index:: Data types, functions, and variables.
@detailmenu
--- The Detailed Node Listing ---
Installation
* Requirements:: Software needed to build and run Guix.
* Setting Up the Daemon:: Preparing the build daemon's environment.
* Invoking guix-daemon:: Running the build daemon.
Setting Up the Daemon
* Build Environment Setup:: Preparing the isolated build environment.
* Daemon Offload Setup:: Offloading builds to remote machines.
Package Management
* Features:: How Guix will make your life brighter.
* Invoking guix package:: Package installation, removal, etc.
* Emacs Interface:: Package management from Emacs.
* Substitutes:: Downloading pre-built binaries.
* Packages with Multiple Outputs:: Single source package, multiple outputs.
* Invoking guix gc:: Running the garbage collector.
* Invoking guix pull:: Fetching the latest Guix and distribution.
* Invoking guix archive:: Exporting and importing store files.
Programming Interface
* Defining Packages:: Defining new packages.
* Build Systems:: Specifying how packages are built.
* The Store:: Manipulating the package store.
* Derivations:: Low-level interface to package derivations.
* The Store Monad:: Purely functional interface to the store.
* G-Expressions:: Manipulating build expressions.
Utilities
* Invoking guix build:: Building packages from the command line.
* Invoking guix download:: Downloading a file and printing its hash.
* Invoking guix hash:: Computing the cryptographic hash of a file.
* Invoking guix import:: Importing package definitions.
* Invoking guix refresh:: Updating package definitions.
* Invoking guix lint:: Finding errors in package definitions.
* Invoking guix environment:: Setting up development environments.
GNU Distribution
* System Installation:: Installing the whole operating system.
* System Configuration:: Configuring the operating system.
* Installing Debugging Files:: Feeding the debugger.
* Security Updates:: Deploying security fixes quickly.
* Package Modules:: Packages from the programmer's viewpoint.
* Packaging Guidelines:: Growing the distribution.
* Bootstrapping:: GNU/Linux built from scratch.
* Porting:: Targeting another platform or kernel.
System Configuration
* Using the Configuration System:: Customizing your GNU system.
* operating-system Reference:: Detail of operating-system declarations.
* File Systems:: Configuring file system mounts.
* Mapped Devices:: Block device extra processing.
* User Accounts:: Specifying user accounts.
* Locales:: Language and cultural convention settings.
* Services:: Specifying system services.
* Setuid Programs:: Programs running with root privileges.
* Name Service Switch:: Configuring libc's name service switch.
* Initial RAM Disk:: Linux-Libre bootstrapping.
* GRUB Configuration:: Configuring the boot loader.
* Invoking guix system:: Instantiating a system configuration.
* Defining Services:: Adding new service definitions.
Services
* Base Services:: Essential system services.
* Networking Services:: Network setup, SSH daemon, etc.
* X Window:: Graphical display.
Packaging Guidelines
* Software Freedom:: What may go into the distribution.
* Package Naming:: What's in a name?
* Version Numbers:: When the name is not enough.
* Python Modules:: Taming the snake.
* Perl Modules:: Little pearls.
* Fonts:: Fond of fonts.
@end detailmenu
@end menu
@c *********************************************************************
@node Introduction
@chapter Introduction
GNU Guix@footnote{``Guix'' is pronounced like ``geeks'', or ``ɡiːks''
using the international phonetic alphabet (IPA).} is a functional
package management tool for the GNU system. Package management consists
of all activities that relate to building packages from sources,
honoring their build-time and run-time dependencies,
installing packages in user environments, upgrading installed packages
to new versions or rolling back to a previous set, removing unused
software packages, etc.
@cindex functional package management
The term @dfn{functional} refers to a specific package management
discipline. In Guix, the package build and installation process is seen
as a function, in the mathematical sense. That function takes inputs,
such as build scripts, a compiler, and libraries, and
returns an installed package. As a pure function, its result depends
solely on its inputs---for instance, it cannot refer to software or
scripts that were not explicitly passed as inputs. A build function
always produces the same result when passed a given set of inputs. It
cannot alter the system's environment in
any way; for instance, it cannot create, modify, or delete files outside
of its build and installation directories. This is achieved by running
build processes in isolated environments (or @dfn{containers}), where only their
explicit inputs are visible.
@cindex store
The result of package build functions is @dfn{cached} in the file
system, in a special directory called @dfn{the store} (@pxref{The
Store}). Each package is installed in a directory of its own, in the
store---by default under @file{/gnu/store}. The directory name contains
a hash of all the inputs used to build that package; thus, changing an
input yields a different directory name.
This approach is the foundation of Guix's salient features: support for
transactional package upgrade and rollback, per-user installation, and
garbage collection of packages (@pxref{Features}).
Guix has a command-line interface, which allows users to build, install,
upgrade, and remove packages, as well as a Scheme programming interface.
@cindex Guix System Distribution
@cindex GSD
Last but not least, Guix is used to build a distribution of the GNU
system, with many GNU and non-GNU free software packages. The Guix
System Distribution, or GNU@tie{}GSD, takes advantage of the core
properties of Guix at the system level. With GNU@tie{}GSD, users
@emph{declare} all aspects of the operating system configuration, and
Guix takes care of instantiating that configuration in a reproducible,
stateless fashion. @xref{GNU Distribution}.
@c *********************************************************************
@node Installation
@chapter Installation
GNU Guix is available for download from its website at
@url{http://www.gnu.org/software/guix/}. This section describes the
software requirements of Guix, as well as how to install it and get
ready to use it.
Note that this section is concerned with the installation of the package
manager, which can be done on top of a running GNU/Linux system. If,
instead, you want to install the complete GNU operating system,
@pxref{System Installation}.
The build procedure for Guix is the same as for other GNU software, and
is not covered here. Please see the files @file{README} and
@file{INSTALL} in the Guix source tree for additional details.
@menu
* Requirements:: Software needed to build and run Guix.
* Setting Up the Daemon:: Preparing the build daemon's environment.
* Invoking guix-daemon:: Running the build daemon.
@end menu
@node Requirements
@section Requirements
GNU Guix depends on the following packages:
@itemize
@item @url{http://gnu.org/software/guile/, GNU Guile}, version 2.0.5 or later;
@item @url{http://gnupg.org/, GNU libgcrypt};
@end itemize
The following dependencies are optional:
@itemize
@item
Installing
@url{http://savannah.nongnu.org/projects/guile-json/, Guile-JSON} will
allow you to use the @command{guix import pypi} command (@pxref{Invoking
guix import}). It is of
interest primarily for developers and not for casual users.
@item
Installing @uref{http://gnutls.org/, GnuTLS-Guile} will
allow you to access @code{https} URLs with the @command{guix download}
command (@pxref{Invoking guix download}), the @command{guix import pypi}
command, and the @command{guix import cpan} command. This is primarily
of interest to developers. @xref{Guile Preparations, how to install the
GnuTLS bindings for Guile,, gnutls-guile, GnuTLS-Guile}.
@end itemize
Unless @code{--disable-daemon} was passed to @command{configure}, the
following packages are also needed:
@itemize
@item @url{http://sqlite.org, SQLite 3}
@item @url{http://www.bzip.org, libbz2}
@item @url{http://gcc.gnu.org, GCC's g++}
@end itemize
When a working installation of @url{http://nixos.org/nix/, the Nix package
manager} is available, you
can instead configure Guix with @code{--disable-daemon}. In that case,
Nix replaces the three dependencies above.
Guix is compatible with Nix, so it is possible to share the same store
between both. To do so, you must pass @command{configure} not only the
same @code{--with-store-dir} value, but also the same
@code{--localstatedir} value. The latter is essential because it
specifies where the database that stores metadata about the store is
located, among other things. The default values for Nix are
@code{--with-store-dir=/nix/store} and @code{--localstatedir=/nix/var}.
Note that @code{--disable-daemon} is not required if
your goal is to share the store with Nix.
@node Setting Up the Daemon
@section Setting Up the Daemon
@cindex daemon
Operations such as building a package or running the garbage collector
are all performed by a specialized process, the @dfn{build daemon}, on
behalf of clients. Only the daemon may access the store and its
associated database. Thus, any operation that manipulates the store
goes through the daemon. For instance, command-line tools such as
@command{guix package} and @command{guix build} communicate with the
daemon (@i{via} remote procedure calls) to instruct it what to do.
The following sections explain how to prepare the build daemon's
environment.
@menu
* Build Environment Setup:: Preparing the isolated build environment.
* Daemon Offload Setup:: Offloading builds to remote machines.
@end menu
@node Build Environment Setup
@subsection Build Environment Setup
In a standard multi-user setup, Guix and its daemon---the
@command{guix-daemon} program---are installed by the system
administrator; @file{/gnu/store} is owned by @code{root} and
@command{guix-daemon} runs as @code{root}. Unprivileged users may use
Guix tools to build packages or otherwise access the store, and the
daemon will do it on their behalf, ensuring that the store is kept in a
consistent state, and allowing built packages to be shared among users.
@cindex build users
When @command{guix-daemon} runs as @code{root}, you may not want package
build processes themselves to run as @code{root} too, for obvious
security reasons. To avoid that, a special pool of @dfn{build users}
should be created for use by build processes started by the daemon.
These build users need not have a shell and a home directory: they will
just be used when the daemon drops @code{root} privileges in build
processes. Having several such users allows the daemon to launch
distinct build processes under separate UIDs, which guarantees that they
do not interfere with each other---an essential feature since builds are
regarded as pure functions (@pxref{Introduction}).
On a GNU/Linux system, a build user pool may be created like this (using
Bash syntax and the @code{shadow} commands):
@c See http://lists.gnu.org/archive/html/bug-guix/2013-01/msg00239.html
@c for why `-G' is needed.
@example
# groupadd guix-builder
# for i in `seq 1 10`;
do
useradd -g guix-builder -G guix-builder \
-d /var/empty -s `which nologin` \
-c "Guix build user $i" --system \
guix-builder$i;
done
@end example
The @file{/gnu/store} directory (or whichever was specified with the
@code{--with-store-dir} option) must have ownership and permissions as
follows:
@example
# chgrp guix-builder /gnu/store
# chmod 1775 /gnu/store
@end example
@noindent
The @code{guix-daemon} program may then be run as @code{root} with:
@example
# guix-daemon --build-users-group=guix-builder
@end example
@cindex chroot
@noindent
This way, the daemon starts build processes in a chroot, under one of
the @code{guix-builder} users. On GNU/Linux, by default, the chroot
environment contains nothing but:
@c Keep this list in sync with libstore/build.cc! -----------------------
@itemize
@item
a minimal @code{/dev} directory, created mostly independently from the
host @code{/dev}@footnote{``Mostly'', because while the set of files
that appear in the chroot's @code{/dev} is fixed, most of these files
can only be created if the host has them.};
@item
the @code{/proc} directory; it only shows the container's processes
since a separate PID name space is used;
@item
@file{/etc/passwd} with an entry for the current user and an entry for
user @file{nobody};
@item
@file{/etc/group} with an entry for the user's group;
@item
@file{/etc/hosts} with an entry that maps @code{localhost} to
@code{127.0.0.1};
@item
a writable @file{/tmp} directory.
@end itemize
If you are installing Guix as an unprivileged user, it is still
possible to run @command{guix-daemon}. However, build processes will
not be isolated from one another, and not from the rest of the system.
Thus, build processes may interfere with each other, and may access
programs, libraries, and other files available on the system---making it
much harder to view them as @emph{pure} functions.
@node Daemon Offload Setup
@subsection Using the Offload Facility
@cindex offloading
@cindex build hook
When desired, the build daemon can @dfn{offload}
derivation builds to other machines
running Guix, using the @code{offload} @dfn{build hook}. When that
feature is enabled, a list of user-specified build machines is read from
@file{/etc/guix/machines.scm}; anytime a build is requested, for
instance via @code{guix build}, the daemon attempts to offload it to one
of the machines that satisfies the derivation's constraints, in
particular its system type---e.g., @file{x86_64-linux}. Missing
prerequisites for the build are copied over SSH to the target machine,
which then proceeds with the build; upon success the output(s) of the
build are copied back to the initial machine.
The @file{/etc/guix/machines.scm} file typically looks like this:
@example
(list (build-machine
(name "eightysix.example.org")
(system "x86_64-linux")
(user "bob")
(speed 2.)) ; incredibly fast!
(build-machine
(name "meeps.example.org")
(system "mips64el-linux")
(user "alice")
(private-key
(string-append (getenv "HOME")
"/.ssh/id-rsa-for-guix"))))
@end example
@noindent
In the example above we specify a list of two build machines, one for
the @code{x86_64} architecture and one for the @code{mips64el}
architecture.
In fact, this file is---not surprisingly!---a Scheme file that is
evaluated when the @code{offload} hook is started. Its return value
must be a list of @code{build-machine} objects. While this example
shows a fixed list of build machines, one could imagine, say, using
DNS-SD to return a list of potential build machines discovered in the
local network (@pxref{Introduction, Guile-Avahi,, guile-avahi, Using
Avahi in Guile Scheme Programs}). The @code{build-machine} data type is
detailed below.
@deftp {Data Type} build-machine
This data type represents build machines the daemon may offload builds
to. The important fields are:
@table @code
@item name
The remote machine's host name.
@item system
The remote machine's system type---e.g., @code{"x86_64-linux"}.
@item user
The user account to use when connecting to the remote machine over SSH.
Note that the SSH key pair must @emph{not} be passphrase-protected, to
allow non-interactive logins.
@end table
A number of optional fields may be specified:
@table @code
@item port
Port number of the machine's SSH server (default: 22).
@item private-key
The SSH private key file to use when connecting to the machine.
@item parallel-builds
The number of builds that may run in parallel on the machine (1 by
default.)
@item speed
A ``relative speed factor''. The offload scheduler will tend to prefer
machines with a higher speed factor.
@item features
A list of strings denoting specific features supported by the machine.
An example is @code{"kvm"} for machines that have the KVM Linux modules
and corresponding hardware support. Derivations can request features by
name, and they will be scheduled on matching build machines.
@end table
@end deftp
The @code{guix} command must be in the search path on the build
machines, since offloading works by invoking the @code{guix archive} and
@code{guix build} commands.
There's one last thing to do once @file{machines.scm} is in place. As
explained above, when offloading, files are transferred back and forth
between the machine stores. For this to work, you need to generate a
key pair to allow the daemon to export signed archives of files from the
store (@pxref{Invoking guix archive}):
@example
# guix archive --generate-key
@end example
@noindent
Thus, when receiving files, a machine's build daemon can make sure they
are genuine, have not been tampered with, and that they are signed by an
authorized key.
@node Invoking guix-daemon
@section Invoking @command{guix-daemon}
The @command{guix-daemon} program implements all the functionality to
access the store. This includes launching build processes, running the
garbage collector, querying the availability of a build result, etc. It
is normally run as @code{root} like this:
@example
# guix-daemon --build-users-group=guix-builder
@end example
@noindent
For details on how to set it up, @pxref{Setting Up the Daemon}.
@cindex chroot
@cindex container, build environment
@cindex build environment
@cindex reproducible builds
By default, @command{guix-daemon} launches build processes under
different UIDs, taken from the build group specified with
@code{--build-users-group}. In addition, each build process is run in a
chroot environment that only contains the subset of the store that the
build process depends on, as specified by its derivation
(@pxref{Programming Interface, derivation}), plus a set of specific
system directories. By default, the latter contains @file{/dev} and
@file{/dev/pts}. Furthermore, on GNU/Linux, the build environment is a
@dfn{container}: in addition to having its own file system tree, it has
a separate mount name space, its own PID name space, network name space,
etc. This helps achieve reproducible builds (@pxref{Features}).
When the daemon performs a build on behalf of the user, it creates a
build directory under @file{/tmp} or under the directory specified by
its @code{TMPDIR} environment variable; this directory is shared with
the container for the duration of the build. Be aware that using a
directory other than @file{/tmp} can affect build results---for example,
with a longer directory name, a build process that uses Unix-domain
sockets might hit the name length limitation for @code{sun_path}, which
it would otherwise not hit.
The build directory is automatically deleted upon completion, unless the
build failed and the client specified @option{--keep-failed}
(@pxref{Invoking guix build, @option{--keep-failed}}).
The following command-line options are supported:
@table @code
@item --build-users-group=@var{group}
Take users from @var{group} to run build processes (@pxref{Setting Up
the Daemon, build users}).
@item --no-substitutes
@cindex substitutes
Do not use substitutes for build products. That is, always build things
locally instead of allowing downloads of pre-built binaries
(@pxref{Substitutes}).
By default substitutes are used, unless the client---such as the
@command{guix package} command---is explicitly invoked with
@code{--no-substitutes}.
When the daemon runs with @code{--no-substitutes}, clients can still
explicitly enable substitution @i{via} the @code{set-build-options}
remote procedure call (@pxref{The Store}).
@item --substitute-urls=@var{urls}
Consider @var{urls} the default whitespace-separated list of substitute
source URLs. When this option is omitted, @code{http://hydra.gnu.org}
is used.
This means that substitutes may be downloaded from @var{urls}, as long
as they are signed by a trusted signature (@pxref{Substitutes}).
@cindex build hook
@item --no-build-hook
Do not use the @dfn{build hook}.
The build hook is a helper program that the daemon can start and to
which it submits build requests. This mechanism is used to offload
builds to other machines (@pxref{Daemon Offload Setup}).
@item --cache-failures
Cache build failures. By default, only successful builds are cached.
@item --cores=@var{n}
@itemx -c @var{n}
Use @var{n} CPU cores to build each derivation; @code{0} means as many
as available.
The default value is @code{0}, but it may be overridden by clients, such
as the @code{--cores} option of @command{guix build} (@pxref{Invoking
guix build}).
The effect is to define the @code{NIX_BUILD_CORES} environment variable
in the build process, which can then use it to exploit internal
parallelism---for instance, by running @code{make -j$NIX_BUILD_CORES}.
@item --max-jobs=@var{n}
@itemx -M @var{n}
Allow at most @var{n} build jobs in parallel. The default value is
@code{1}. Setting it to @code{0} means that no builds will be performed
locally; instead, the daemon will offload builds (@pxref{Daemon Offload
Setup}), or simply fail.
@item --debug
Produce debugging output.
This is useful to debug daemon start-up issues, but then it may be
overridden by clients, for example the @code{--verbosity} option of
@command{guix build} (@pxref{Invoking guix build}).
@item --chroot-directory=@var{dir}
Add @var{dir} to the build chroot.
Doing this may change the result of build processes---for instance if
they use optional dependencies found in @var{dir} when it is available,
and not otherwise. For that reason, it is not recommended to do so.
Instead, make sure that each derivation declares all the inputs that it
needs.
@item --disable-chroot
Disable chroot builds.
Using this option is not recommended since, again, it would allow build
processes to gain access to undeclared dependencies.
@item --disable-log-compression
Disable compression of the build logs.
Unless @code{--lose-logs} is used, all the build logs are kept in the
@var{localstatedir}. To save space, the daemon automatically compresses
them with bzip2 by default. This option disables that.
@item --disable-deduplication
@cindex deduplication
Disable automatic file ``deduplication'' in the store.
By default, files added to the store are automatically ``deduplicated'':
if a newly added file is identical to another one found in the store,
the daemon makes the new file a hard link to the other file. This can
noticeably reduce disk usage, at the expense of slightly increasde
input/output load at the end of a build process. This option disables
this optimization.
@item --gc-keep-outputs[=yes|no]
Tell whether the garbage collector (GC) must keep outputs of live
derivations.
When set to ``yes'', the GC will keep the outputs of any live derivation
available in the store---the @code{.drv} files. The default is ``no'',
meaning that derivation outputs are kept only if they are GC roots.
@item --gc-keep-derivations[=yes|no]
Tell whether the garbage collector (GC) must keep derivations
corresponding to live outputs.
When set to ``yes'', as is the case by default, the GC keeps
derivations---i.e., @code{.drv} files---as long as at least one of their
outputs is live. This allows users to keep track of the origins of
items in their store. Setting it to ``no'' saves a bit of disk space.
Note that when both @code{--gc-keep-derivations} and
@code{--gc-keep-outputs} are used, the effect is to keep all the build
prerequisites (the sources, compiler, libraries, and other build-time
tools) of live objects in the store, regardless of whether these
prerequisites are live. This is convenient for developers since it
saves rebuilds or downloads.
@item --impersonate-linux-2.6
On Linux-based systems, impersonate Linux 2.6. This means that the
kernel's @code{uname} system call will report 2.6 as the release number.
This might be helpful to build programs that (usually wrongfully) depend
on the kernel version number.
@item --lose-logs
Do not keep build logs. By default they are kept under
@code{@var{localstatedir}/guix/log}.
@item --system=@var{system}
Assume @var{system} as the current system type. By default it is the
architecture/kernel pair found at configure time, such as
@code{x86_64-linux}.
@item --listen=@var{socket}
Listen for connections on @var{socket}, the file name of a Unix-domain
socket. The default socket is
@file{@var{localstatedir}/daemon-socket/socket}. This option is only
useful in exceptional circumstances, such as if you need to run several
daemons on the same machine.
@end table
@c *********************************************************************
@node Package Management
@chapter Package Management
The purpose of GNU Guix is to allow users to easily install, upgrade, and
remove software packages, without having to know about their build
procedure or dependencies. Guix also goes beyond this obvious set of
features.
This chapter describes the main features of Guix, as well as the package
management tools it provides. Two user interfaces are provided for
routine package management tasks: a command-line interface
(@pxref{Invoking guix package, @code{guix package}}), and a visual user
interface in Emacs (@pxref{Emacs Interface}).
@menu
* Features:: How Guix will make your life brighter.
* Invoking guix package:: Package installation, removal, etc.
* Emacs Interface:: Package management from Emacs.
* Substitutes:: Downloading pre-built binaries.
* Packages with Multiple Outputs:: Single source package, multiple outputs.
* Invoking guix gc:: Running the garbage collector.
* Invoking guix pull:: Fetching the latest Guix and distribution.
* Invoking guix archive:: Exporting and importing store files.
@end menu
@node Features
@section Features
When using Guix, each package ends up in the @dfn{package store}, in its
own directory---something that resembles
@file{/gnu/store/xxx-package-1.2}, where @code{xxx} is a base32 string
(note that Guix comes with an Emacs extension to shorten those file
names, @pxref{Emacs Prettify}.)
Instead of referring to these directories, users have their own
@dfn{profile}, which points to the packages that they actually want to
use. These profiles are stored within each user's home directory, at
@code{$HOME/.guix-profile}.
For example, @code{alice} installs GCC 4.7.2. As a result,
@file{/home/alice/.guix-profile/bin/gcc} points to
@file{/gnu/store/@dots{}-gcc-4.7.2/bin/gcc}. Now, on the same machine,
@code{bob} had already installed GCC 4.8.0. The profile of @code{bob}
simply continues to point to
@file{/gnu/store/@dots{}-gcc-4.8.0/bin/gcc}---i.e., both versions of GCC
coexist on the same system without any interference.
The @command{guix package} command is the central tool to manage
packages (@pxref{Invoking guix package}). It operates on those per-user
profiles, and can be used @emph{with normal user privileges}.
The command provides the obvious install, remove, and upgrade
operations. Each invocation is actually a @emph{transaction}: either
the specified operation succeeds, or nothing happens. Thus, if the
@command{guix package} process is terminated during the transaction,
or if a power outage occurs during the transaction, then the user's
profile remains in its previous state, and remains usable.
In addition, any package transaction may be @emph{rolled back}. So, if,
for example, an upgrade installs a new version of a package that turns
out to have a serious bug, users may roll back to the previous instance
of their profile, which was known to work well. Similarly, the global
system configuration is subject to transactional upgrades and roll-back
(@pxref{Using the Configuration System}).
All those packages in the package store may be @emph{garbage-collected}.
Guix can determine which packages are still referenced by the user
profiles, and remove those that are provably no longer referenced
(@pxref{Invoking guix gc}). Users may also explicitly remove old
generations of their profile so that the packages they refer to can be
collected.
@cindex reproducibility
@cindex reproducible builds
Finally, Guix takes a @dfn{purely functional} approach to package
management, as described in the introduction (@pxref{Introduction}).
Each @file{/gnu/store} package directory name contains a hash of all the
inputs that were used to build that package---compiler, libraries, build
scripts, etc. This direct correspondence allows users to make sure a
given package installation matches the current state of their
distribution. It also helps maximize @dfn{build reproducibility}:
thanks to the isolated build environments that are used, a given build
is likely to yield bit-identical files when performed on different
machines (@pxref{Invoking guix-daemon, container}).
@cindex substitutes
This foundation allows Guix to support @dfn{transparent binary/source
deployment}. When a pre-built binary for a @file{/gnu/store} item is
available from an external source---a @dfn{substitute}, Guix just
downloads it and unpacks it;
otherwise, it builds the package from source, locally
(@pxref{Substitutes}).
Control over the build environment is a feature that is also useful for
developers. The @command{guix environment} command allows developers of
a package to quickly set up the right development environment for their
package, without having to manually install the package's dependencies
in their profile (@pxref{Invoking guix environment}).
@node Invoking guix package
@section Invoking @command{guix package}
The @command{guix package} command is the tool that allows users to
install, upgrade, and remove packages, as well as rolling back to
previous configurations. It operates only on the user's own profile,
and works with normal user privileges (@pxref{Features}). Its syntax
is:
@example
guix package @var{options}
@end example
Primarily, @var{options} specifies the operations to be performed during
the transaction. Upon completion, a new profile is created, but
previous generations of the profile remain available, should the user
want to roll back.
For example, to remove @code{lua} and install @code{guile} and
@code{guile-cairo} in a single transaction:
@example
guix package -r lua -i guile guile-cairo
@end example
For each user, a symlink to the user's default profile is automatically
created in @file{$HOME/.guix-profile}. This symlink always points to the
current generation of the user's default profile. Thus, users can add
@file{$HOME/.guix-profile/bin} to their @code{PATH} environment
variable, and so on.
In a multi-user setup, user profiles are stored in a place registered as
a @dfn{garbage-collector root}, which @file{$HOME/.guix-profile} points
to (@pxref{Invoking guix gc}). That directory is normally
@code{@var{localstatedir}/profiles/per-user/@var{user}}, where
@var{localstatedir} is the value passed to @code{configure} as
@code{--localstatedir}, and @var{user} is the user name. The
@file{per-user} directory is created when @command{guix-daemon} is
started, and the @var{user} sub-directory is created by @command{guix
package}.
The @var{options} can be among the following:
@table @code
@item --install=@var{package} @dots{}
@itemx -i @var{package} @dots{}
Install the specified @var{package}s.
Each @var{package} may specify either a simple package name, such as
@code{guile}, or a package name followed by a hyphen and version number,
such as @code{guile-1.8.8}. If no version number is specified, the
newest available version will be selected. In addition, @var{package}
may contain a colon, followed by the name of one of the outputs of the
package, as in @code{gcc:doc} or @code{binutils-2.22:lib}
(@pxref{Packages with Multiple Outputs}). Packages with a corresponding
name (and optionally version) are searched for among the GNU
distribution modules (@pxref{Package Modules}).
@cindex propagated inputs
Sometimes packages have @dfn{propagated inputs}: these are dependencies
that automatically get installed along with the required package.
An example is the GNU MPC library: its C header files refer to those of
the GNU MPFR library, which in turn refer to those of the GMP library.
Thus, when installing MPC, the MPFR and GMP libraries also get installed
in the profile; removing MPC also removes MPFR and GMP---unless they had
also been explicitly installed independently.
Besides, packages sometimes rely on the definition of environment
variables for their search paths (see explanation of
@code{--search-paths} below). Any missing or possibly incorrect
environment variable definitions are reported here.
@c XXX: keep me up-to-date
Finally, when installing a GNU package, the tool reports the
availability of a newer upstream version. In the future, it may provide
the option of installing directly from the upstream version, even if
that version is not yet in the distribution.
@item --install-from-expression=@var{exp}
@itemx -e @var{exp}
Install the package @var{exp} evaluates to.
@var{exp} must be a Scheme expression that evaluates to a
@code{<package>} object. This option is notably useful to disambiguate
between same-named variants of a package, with expressions such as
@code{(@@ (gnu packages base) guile-final)}.
Note that this option installs the first output of the specified
package, which may be insufficient when needing a specific output of a
multiple-output package.
@item --remove=@var{package} @dots{}
@itemx -r @var{package} @dots{}
Remove the specified @var{package}s.
As for @code{--install}, each @var{package} may specify a version number
and/or output name in addition to the package name. For instance,
@code{-r glibc:debug} would remove the @code{debug} output of
@code{glibc}.
@item --upgrade[=@var{regexp} @dots{}]
@itemx -u [@var{regexp} @dots{}]
Upgrade all the installed packages. If one or more @var{regexp}s are
specified, upgrade only installed packages whose name matches a
@var{regexp}.
Note that this upgrades package to the latest version of packages found
in the distribution currently installed. To update your distribution,
you should regularly run @command{guix pull} (@pxref{Invoking guix
pull}).
@item --roll-back
Roll back to the previous @dfn{generation} of the profile---i.e., undo
the last transaction.
When combined with options such as @code{--install}, roll back occurs
before any other actions.
When rolling back from the first generation that actually contains
installed packages, the profile is made to point to the @dfn{zeroth
generation}, which contains no files apart from its own meta-data.
Installing, removing, or upgrading packages from a generation that has
been rolled back to overwrites previous future generations. Thus, the
history of a profile's generations is always linear.
@item --switch-generation=@var{pattern}
@itemx -S @var{pattern}
Switch to a particular generation defined by @var{pattern}.
@var{pattern} may be either a generation number or a number prefixed
with ``+'' or ``-''. The latter means: move forward/backward by a
specified number of generations. For example, if you want to return to
the latest generation after @code{--roll-back}, use
@code{--switch-generation=+1}.
The difference between @code{--roll-back} and
@code{--switch-generation=-1} is that @code{--switch-generation} will
not make a zeroth generation, so if a specified generation does not
exist, the current generation will not be changed.
@item --search-paths
@cindex search paths
Report environment variable definitions, in Bash syntax, that may be
needed in order to use the set of installed packages. These environment
variables are used to specify @dfn{search paths} for files used by some
of the installed packages.
For example, GCC needs the @code{CPATH} and @code{LIBRARY_PATH}
environment variables to be defined so it can look for headers and
libraries in the user's profile (@pxref{Environment Variables,,, gcc,
Using the GNU Compiler Collection (GCC)}). If GCC and, say, the C
library are installed in the profile, then @code{--search-paths} will
suggest setting these variables to @code{@var{profile}/include} and
@code{@var{profile}/lib}, respectively.
@item --profile=@var{profile}
@itemx -p @var{profile}
Use @var{profile} instead of the user's default profile.
@item --verbose
Produce verbose output. In particular, emit the environment's build log
on the standard error port.
@item --bootstrap
Use the bootstrap Guile to build the profile. This option is only
useful to distribution developers.
@end table
In addition to these actions @command{guix package} supports the
following options to query the current state of a profile, or the
availability of packages:
@table @option
@item --search=@var{regexp}
@itemx -s @var{regexp}
List the available packages whose synopsis or description matches
@var{regexp}. Print all the meta-data of matching packages in
@code{recutils} format (@pxref{Top, GNU recutils databases,, recutils,
GNU recutils manual}).
This allows specific fields to be extracted using the @command{recsel}
command, for instance:
@example
$ guix package -s malloc | recsel -p name,version
name: glibc
version: 2.17
name: libgc
version: 7.2alpha6
@end example
Similarly, to show the name of all the packages available under the
terms of the GNU@tie{}LGPL version 3:
@example
$ guix package -s "" | recsel -p name -e 'license ~ "LGPL 3"'
name: elfutils
name: gmp
@dots{}
@end example
@item --show=@var{package}
Show details about @var{package}, taken from the list of available packages, in
@code{recutils} format (@pxref{Top, GNU recutils databases,, recutils, GNU
recutils manual}).
@example
$ guix package --show=python | recsel -p name,version
name: python
version: 2.7.6
name: python
version: 3.3.5
@end example
You may also specify the full name of a package to only get details about a
specific version of it:
@example
$ guix package --show=python-3.3.5 | recsel -p name,version
name: python
version: 3.3.5
@end example
@item --list-installed[=@var{regexp}]
@itemx -I [@var{regexp}]
List the currently installed packages in the specified profile, with the
most recently installed packages shown last. When @var{regexp} is
specified, list only installed packages whose name matches @var{regexp}.
For each installed package, print the following items, separated by
tabs: the package name, its version string, the part of the package that
is installed (for instance, @code{out} for the default output,
@code{include} for its headers, etc.), and the path of this package in
the store.
@item --list-available[=@var{regexp}]
@itemx -A [@var{regexp}]
List packages currently available in the software distribution
(@pxref{GNU Distribution}). When @var{regexp} is specified, list only
installed packages whose name matches @var{regexp}.
For each package, print the following items separated by tabs: its name,
its version string, the parts of the package (@pxref{Packages with
Multiple Outputs}), and the source location of its definition.
@item --list-generations[=@var{pattern}]
@itemx -l [@var{pattern}]
Return a list of generations along with their creation dates; for each
generation, show the installed packages, with the most recently
installed packages shown last. Note that the zeroth generation is never
shown.
For each installed package, print the following items, separated by
tabs: the name of a package, its version string, the part of the package
that is installed (@pxref{Packages with Multiple Outputs}), and the
location of this package in the store.
When @var{pattern} is used, the command returns only matching
generations. Valid patterns include:
@itemize
@item @emph{Integers and comma-separated integers}. Both patterns denote
generation numbers. For instance, @code{--list-generations=1} returns
the first one.
And @code{--list-generations=1,8,2} outputs three generations in the
specified order. Neither spaces nor trailing commas are allowed.
@item @emph{Ranges}. @code{--list-generations=2..9} prints the
specified generations and everything in between. Note that the start of
a range must be lesser than its end.
It is also possible to omit the endpoint. For example,
@code{--list-generations=2..}, returns all generations starting from the
second one.
@item @emph{Durations}. You can also get the last @emph{N}@tie{}days, weeks,
or months by passing an integer along with the first letter of the
duration. For example, @code{--list-generations=20d} lists generations
that are up to 20 days old.
@end itemize
@item --delete-generations[=@var{pattern}]
@itemx -d [@var{pattern}]
When @var{pattern} is omitted, delete all generations except the current
one.
This command accepts the same patterns as @option{--list-generations}.
When @var{pattern} is specified, delete the matching generations. When
@var{pattern} specifies a duration, generations @emph{older} than the
specified duration match. For instance, @code{--delete-generations=1m}
deletes generations that are more than one month old.
If the current generation matches, it is deleted atomically---i.e., by
switching to the previous available generation. Note that the zeroth
generation is never deleted.
Note that deleting generations prevents roll-back to them.
Consequently, this command must be used with care.
@end table
Finally, since @command{guix package} may actually start build
processes, it supports all the common build options that @command{guix
build} supports (@pxref{Invoking guix build, common build options}).
@include emacs.texi
@node Substitutes
@section Substitutes
@cindex substitutes
@cindex pre-built binaries
Guix supports transparent source/binary deployment, which means that it
can either build things locally, or download pre-built items from a
server. We call these pre-built items @dfn{substitutes}---they are
substitutes for local build results. In many cases, downloading a
substitute is much faster than building things locally.
Substitutes can be anything resulting from a derivation build
(@pxref{Derivations}). Of course, in the common case, they are
pre-built package binaries, but source tarballs, for instance, which
also result from derivation builds, can be available as substitutes.
The @code{hydra.gnu.org} server is a front-end to a build farm that
builds packages from the GNU distribution continuously for some
architectures, and makes them available as substitutes. This is the
default source of substitutes; it can be overridden by passing
@command{guix-daemon} the @code{--substitute-urls} option
(@pxref{Invoking guix-daemon}).
@cindex security
@cindex digital signatures
To allow Guix to download substitutes from @code{hydra.gnu.org}, you
must add its public key to the access control list (ACL) of archive
imports, using the @command{guix archive} command (@pxref{Invoking guix
archive}). Doing so implies that you trust @code{hydra.gnu.org} to not
be compromised and to serve genuine substitutes.
This public key is installed along with Guix, in
@code{@var{prefix}/share/guix/hydra.gnu.org.pub}, where @var{prefix} is
the installation prefix of Guix. If you installed Guix from source,
make sure you checked the GPG signature of
@file{guix-@value{VERSION}.tar.gz}, which contains this public key file.
Then, you can run something like this:
@example
# guix archive --authorize < hydra.gnu.org.pub
@end example
Once this is in place, the output of a command like @code{guix build}
should change from something like:
@example
$ guix build emacs --dry-run
The following derivations would be built:
/gnu/store/yr7bnx8xwcayd6j95r2clmkdl1qh688w-emacs-24.3.drv
/gnu/store/x8qsh1hlhgjx6cwsjyvybnfv2i37z23w-dbus-1.6.4.tar.gz.drv
/gnu/store/1ixwp12fl950d15h2cj11c73733jay0z-alsa-lib-1.0.27.1.tar.bz2.drv
/gnu/store/nlma1pw0p603fpfiqy7kn4zm105r5dmw-util-linux-2.21.drv
@dots{}
@end example
@noindent
to something like:
@example
$ guix build emacs --dry-run
The following files would be downloaded:
/gnu/store/pk3n22lbq6ydamyymqkkz7i69wiwjiwi-emacs-24.3
/gnu/store/2ygn4ncnhrpr61rssa6z0d9x22si0va3-libjpeg-8d
/gnu/store/71yz6lgx4dazma9dwn2mcjxaah9w77jq-cairo-1.12.16
/gnu/store/7zdhgp0n1518lvfn8mb96sxqfmvqrl7v-libxrender-0.9.7
@dots{}
@end example
@noindent
This indicates that substitutes from @code{hydra.gnu.org} are usable and
will be downloaded, when possible, for future builds.
Guix ignores substitutes that are not signed, or that are not signed by
one of the keys listed in the ACL. It also detects and raises an error
when attempting to use a substitute that has been tampered with.
The substitute mechanism can be disabled globally by running
@code{guix-daemon} with @code{--no-substitutes} (@pxref{Invoking
guix-daemon}). It can also be disabled temporarily by passing the
@code{--no-substitutes} option to @command{guix package}, @command{guix
build}, and other command-line tools.
Today, each individual's control over their own computing is at the
mercy of institutions, corporations, and groups with enough power and
determination to subvert the computing infrastructure and exploit its
weaknesses. While using @code{hydra.gnu.org} substitutes can be
convenient, we encourage users to also build on their own, or even run
their own build farm, such that @code{hydra.gnu.org} is less of an
interesting target.
Guix has the foundations to maximize build reproducibility
(@pxref{Features}). In most cases, independent builds of a given
package or derivation should yield bit-identical results. Thus, through
a diverse set of independent package builds, we can strengthen the
integrity of our systems.
In the future, we want Guix to have support to publish and retrieve
binaries to/from other users, in a peer-to-peer fashion. If you would
like to discuss this project, join us on @email{guix-devel@@gnu.org}.
@node Packages with Multiple Outputs
@section Packages with Multiple Outputs
@cindex multiple-output packages
@cindex package outputs
Often, packages defined in Guix have a single @dfn{output}---i.e., the
source package leads exactly one directory in the store. When running
@command{guix package -i glibc}, one installs the default output of the
GNU libc package; the default output is called @code{out}, but its name
can be omitted as shown in this command. In this particular case, the
default output of @code{glibc} contains all the C header files, shared
libraries, static libraries, Info documentation, and other supporting
files.
Sometimes it is more appropriate to separate the various types of files
produced from a single source package into separate outputs. For
instance, the GLib C library (used by GTK+ and related packages)
installs more than 20 MiB of reference documentation as HTML pages.
To save space for users who do not need it, the documentation goes to a
separate output, called @code{doc}. To install the main GLib output,
which contains everything but the documentation, one would run:
@example
guix package -i glib
@end example
The command to install its documentation is:
@example
guix package -i glib:doc
@end example
Some packages install programs with different ``dependency footprints''.
For instance, the WordNet package install both command-line tools and
graphical user interfaces (GUIs). The former depend solely on the C
library, whereas the latter depend on Tcl/Tk and the underlying X
libraries. In this case, we leave the command-line tools in the default
output, whereas the GUIs are in a separate output. This allows users
who do not need the GUIs to save space.
There are several such multiple-output packages in the GNU distribution.
Other conventional output names include @code{lib} for libraries and
possibly header files, @code{bin} for stand-alone programs, and
@code{debug} for debugging information (@pxref{Installing Debugging
Files}). The outputs of a packages are listed in the third column of
the output of @command{guix package --list-available} (@pxref{Invoking
guix package}).
@node Invoking guix gc
@section Invoking @command{guix gc}
@cindex garbage collector
Packages that are installed but not used may be @dfn{garbage-collected}.
The @command{guix gc} command allows users to explicitly run the garbage
collector to reclaim space from the @file{/gnu/store} directory.
The garbage collector has a set of known @dfn{roots}: any file under
@file{/gnu/store} reachable from a root is considered @dfn{live} and
cannot be deleted; any other file is considered @dfn{dead} and may be
deleted. The set of garbage collector roots includes default user
profiles, and may be augmented with @command{guix build --root}, for
example (@pxref{Invoking guix build}).
Prior to running @code{guix gc --collect-garbage} to make space, it is
often useful to remove old generations from user profiles; that way, old
package builds referenced by those generations can be reclaimed. This
is achieved by running @code{guix package --delete-generations}
(@pxref{Invoking guix package}).
The @command{guix gc} command has three modes of operation: it can be
used to garbage-collect any dead files (the default), to delete specific
files (the @code{--delete} option), or to print garbage-collector
information. The available options are listed below:
@table @code
@item --collect-garbage[=@var{min}]
@itemx -C [@var{min}]
Collect garbage---i.e., unreachable @file{/gnu/store} files and
sub-directories. This is the default operation when no option is
specified.
When @var{min} is given, stop once @var{min} bytes have been collected.
@var{min} may be a number of bytes, or it may include a unit as a
suffix, such as @code{MiB} for mebibytes and @code{GB} for gigabytes
(@pxref{Block size, size specifications,, coreutils, GNU Coreutils}).
When @var{min} is omitted, collect all the garbage.
@item --delete
@itemx -d
Attempt to delete all the store files and directories specified as
arguments. This fails if some of the files are not in the store, or if
they are still live.
@item --list-dead
Show the list of dead files and directories still present in the
store---i.e., files and directories no longer reachable from any root.
@item --list-live
Show the list of live store files and directories.
@end table
In addition, the references among existing store files can be queried:
@table @code
@item --references
@itemx --referrers
List the references (respectively, the referrers) of store files given
as arguments.
@item --requisites
@itemx -R
List the requisites of the store files passed as arguments. Requisites
include the store files themselves, their references, and the references
of these, recursively. In other words, the returned list is the
@dfn{transitive closure} of the store files.
@end table
@node Invoking guix pull
@section Invoking @command{guix pull}
Packages are installed or upgraded to the latest version available in
the distribution currently available on your local machine. To update
that distribution, along with the Guix tools, you must run @command{guix
pull}: the command downloads the latest Guix source code and package
descriptions, and deploys it.
On completion, @command{guix package} will use packages and package
versions from this just-retrieved copy of Guix. Not only that, but all
the Guix commands and Scheme modules will also be taken from that latest
version. New @command{guix} sub-commands added by the update also
become available.
The @command{guix pull} command is usually invoked with no arguments,
but it supports the following options:
@table @code
@item --verbose
Produce verbose output, writing build logs to the standard error output.
@item --url=@var{url}
Download the source tarball of Guix from @var{url}.
By default, the tarball is taken from its canonical address at
@code{gnu.org}, for the stable branch of Guix.
@item --bootstrap
Use the bootstrap Guile to build the latest Guix. This option is only
useful to Guix developers.
@end table
@node Invoking guix archive
@section Invoking @command{guix archive}
The @command{guix archive} command allows users to @dfn{export} files
from the store into a single archive, and to later @dfn{import} them.
In particular, it allows store files to be transferred from one machine
to another machine's store. For example, to transfer the @code{emacs}
package to a machine connected over SSH, one would run:
@example
guix archive --export -r emacs | ssh the-machine guix archive --import
@end example
@noindent
Similarly, a complete user profile may be transferred from one machine
to another like this:
@example
guix archive --export -r $(readlink -f ~/.guix-profile) | \
ssh the-machine guix-archive --import
@end example
@noindent
However, note that, in both examples, all of @code{emacs} and the
profile as well as all of their dependencies are transferred (due to
@code{-r}), regardless of what is already available in the target
machine's store. The @code{--missing} option can help figure out which
items are missing from the target's store.
Archives are stored in the ``Nix archive'' or ``Nar'' format, which is
comparable in spirit to `tar', but with a few noteworthy differences
that make it more appropriate for our purposes. First, rather than
recording all Unix meta-data for each file, the Nar format only mentions
the file type (regular, directory, or symbolic link); Unix permissions
and owner/group are dismissed. Second, the order in which directory
entries are stored always follows the order of file names according to
the C locale collation order. This makes archive production fully
deterministic.
When exporting, the daemon digitally signs the contents of the archive,
and that digital signature is appended. When importing, the daemon
verifies the signature and rejects the import in case of an invalid
signature or if the signing key is not authorized.
@c FIXME: Add xref to daemon doc about signatures.
The main options are:
@table @code
@item --export
Export the specified store files or packages (see below.) Write the
resulting archive to the standard output.
Dependencies are @emph{not} included in the output, unless
@code{--recursive} is passed.
@item -r
@itemx --recursive
When combined with @code{--export}, this instructs @command{guix
archive} to include dependencies of the given items in the archive.
Thus, the resulting archive is self-contained: it contains the closure
of the exported store items.
@item --import
Read an archive from the standard input, and import the files listed
therein into the store. Abort if the archive has an invalid digital
signature, or if it is signed by a public key not among the authorized
keys (see @code{--authorize} below.)
@item --missing
Read a list of store file names from the standard input, one per line,
and write on the standard output the subset of these files missing from
the store.
@item --generate-key[=@var{parameters}]
@cindex signing, archives
Generate a new key pair for the daemons. This is a prerequisite before
archives can be exported with @code{--export}. Note that this operation
usually takes time, because it needs to gather enough entropy to
generate the key pair.
The generated key pair is typically stored under @file{/etc/guix}, in
@file{signing-key.pub} (public key) and @file{signing-key.sec} (private
key, which must be kept secret.) When @var{parameters} is omitted,
an ECDSA key using the Ed25519 curve is generated, or, for Libgcrypt
versions before 1.6.0, it is a 4096-bit RSA key.
Alternately, @var{parameters} can specify
@code{genkey} parameters suitable for Libgcrypt (@pxref{General
public-key related Functions, @code{gcry_pk_genkey},, gcrypt, The
Libgcrypt Reference Manual}).
@item --authorize
@cindex authorizing, archives
Authorize imports signed by the public key passed on standard input.
The public key must be in ``s-expression advanced format''---i.e., the
same format as the @file{signing-key.pub} file.
The list of authorized keys is kept in the human-editable file
@file{/etc/guix/acl}. The file contains
@url{http://people.csail.mit.edu/rivest/Sexp.txt, ``advanced-format
s-expressions''} and is structured as an access-control list in the
@url{http://theworld.com/~cme/spki.txt, Simple Public-Key Infrastructure
(SPKI)}.
@end table
To export store files as an archive to the standard output, run:
@example
guix archive --export @var{options} @var{specifications}...
@end example
@var{specifications} may be either store file names or package
specifications, as for @command{guix package} (@pxref{Invoking guix
package}). For instance, the following command creates an archive
containing the @code{gui} output of the @code{git} package and the main
output of @code{emacs}:
@example
guix archive --export git:gui /gnu/store/...-emacs-24.3 > great.nar
@end example
If the specified packages are not built yet, @command{guix archive}
automatically builds them. The build process may be controlled with the
same options that can be passed to the @command{guix build} command
(@pxref{Invoking guix build, common build options}).
@c *********************************************************************
@node Programming Interface
@chapter Programming Interface
GNU Guix provides several Scheme programming interfaces (APIs) to
define, build, and query packages. The first interface allows users to
write high-level package definitions. These definitions refer to
familiar packaging concepts, such as the name and version of a package,
its build system, and its dependencies. These definitions can then be
turned into concrete build actions.
Build actions are performed by the Guix daemon, on behalf of users. In a
standard setup, the daemon has write access to the store---the
@file{/gnu/store} directory---whereas users do not. The recommended
setup also has the daemon perform builds in chroots, under a specific
build users, to minimize interference with the rest of the system.
@cindex derivation
Lower-level APIs are available to interact with the daemon and the
store. To instruct the daemon to perform a build action, users actually
provide it with a @dfn{derivation}. A derivation is a low-level
representation of the build actions to be taken, and the environment in
which they should occur---derivations are to package definitions what
assembly is to C programs. The term ``derivation'' comes from the fact
that build results @emph{derive} from them.
This chapter describes all these APIs in turn, starting from high-level
package definitions.
@menu
* Defining Packages:: Defining new packages.
* Build Systems:: Specifying how packages are built.
* The Store:: Manipulating the package store.
* Derivations:: Low-level interface to package derivations.
* The Store Monad:: Purely functional interface to the store.
* G-Expressions:: Manipulating build expressions.
@end menu
@node Defining Packages
@section Defining Packages
The high-level interface to package definitions is implemented in the
@code{(guix packages)} and @code{(guix build-system)} modules. As an
example, the package definition, or @dfn{recipe}, for the GNU Hello
package looks like this:
@example
(define-module (gnu packages hello)
#:use-module (guix packages)
#:use-module (guix download)
#:use-module (guix build-system gnu)
#:use-module (guix licenses))
(define-public hello
(package
(name "hello")
(version "2.8")
(source (origin
(method url-fetch)
(uri (string-append "mirror://gnu/hello/hello-" version
".tar.gz"))
(sha256
(base32 "0wqd8sjmxfskrflaxywc7gqw7sfawrfvdxd9skxawzfgyy0pzdz6"))))
(build-system gnu-build-system)
(arguments `(#:configure-flags '("--enable-silent-rules")))
(inputs `(("gawk" ,gawk)))
(synopsis "Hello, GNU world: An example GNU package")
(description "Guess what GNU Hello prints!")
(home-page "http://www.gnu.org/software/hello/")
(license gpl3+)))
@end example
@noindent
Without being a Scheme expert, the reader may have guessed the meaning
of the various fields here. This expression binds variable @code{hello}
to a @code{<package>} object, which is essentially a record
(@pxref{SRFI-9, Scheme records,, guile, GNU Guile Reference Manual}).
This package object can be inspected using procedures found in the
@code{(guix packages)} module; for instance, @code{(package-name hello)}
returns---surprise!---@code{"hello"}.
With luck, you may be able to import part or all of the definition of
the package you are interested in from another repository, using the
@code{guix import} command (@pxref{Invoking guix import}).
In the example above, @var{hello} is defined into a module of its own,
@code{(gnu packages hello)}. Technically, this is not strictly
necessary, but it is convenient to do so: all the packages defined in
modules under @code{(gnu packages @dots{})} are automatically known to
the command-line tools (@pxref{Package Modules}).
There are a few points worth noting in the above package definition:
@itemize
@item
The @code{source} field of the package is an @code{<origin>} object.
Here, the @code{url-fetch} method from @code{(guix download)} is used,
meaning that the source is a file to be downloaded over FTP or HTTP.
The @code{mirror://gnu} prefix instructs @code{url-fetch} to use one of
the GNU mirrors defined in @code{(guix download)}.
The @code{sha256} field specifies the expected SHA256 hash of the file
being downloaded. It is mandatory, and allows Guix to check the
integrity of the file. The @code{(base32 @dots{})} form introduces the
base32 representation of the hash. You can obtain this information with
@code{guix download} (@pxref{Invoking guix download}) and @code{guix
hash} (@pxref{Invoking guix hash}).
@cindex patches
When needed, the @code{origin} form can also have a @code{patches} field
listing patches to be applied, and a @code{snippet} field giving a
Scheme expression to modify the source code.
@item
@cindex GNU Build System
The @code{build-system} field specifies the procedure to build the
package (@pxref{Build Systems}). Here, @var{gnu-build-system}
represents the familiar GNU Build System, where packages may be
configured, built, and installed with the usual @code{./configure &&
make && make check && make install} command sequence.
@item
The @code{arguments} field specifies options for the build system
(@pxref{Build Systems}). Here it is interpreted by
@var{gnu-build-system} as a request run @file{configure} with the
@code{--enable-silent-rules} flag.
@item
The @code{inputs} field specifies inputs to the build process---i.e.,
build-time or run-time dependencies of the package. Here, we define an
input called @code{"gawk"} whose value is that of the @var{gawk}
variable; @var{gawk} is itself bound to a @code{<package>} object.
Note that GCC, Coreutils, Bash, and other essential tools do not need to
be specified as inputs here. Instead, @var{gnu-build-system} takes care
of ensuring that they are present (@pxref{Build Systems}).
However, any other dependencies need to be specified in the
@code{inputs} field. Any dependency not specified here will simply be
unavailable to the build process, possibly leading to a build failure.
@end itemize
Once a package definition is in place, the
package may actually be built using the @code{guix build} command-line
tool (@pxref{Invoking guix build}). @xref{Packaging Guidelines}, for
more information on how to test package definitions, and
@ref{Invoking guix lint}, for information on how to check a definition
for style conformance.
Eventually, updating the package definition to a new upstream version
can be partly automated by the @command{guix refresh} command
(@pxref{Invoking guix refresh}).
Behind the scenes, a derivation corresponding to the @code{<package>}
object is first computed by the @code{package-derivation} procedure.
That derivation is stored in a @code{.drv} file under @file{/gnu/store}.
The build actions it prescribes may then be realized by using the
@code{build-derivations} procedure (@pxref{The Store}).
@deffn {Scheme Procedure} package-derivation @var{store} @var{package} [@var{system}]
Return the @code{<derivation>} object of @var{package} for @var{system}
(@pxref{Derivations}).
@var{package} must be a valid @code{<package>} object, and @var{system}
must be a string denoting the target system type---e.g.,
@code{"x86_64-linux"} for an x86_64 Linux-based GNU system. @var{store}
must be a connection to the daemon, which operates on the store
(@pxref{The Store}).
@end deffn
@noindent
@cindex cross-compilation
Similarly, it is possible to compute a derivation that cross-builds a
package for some other system:
@deffn {Scheme Procedure} package-cross-derivation @var{store} @
@var{package} @var{target} [@var{system}]
Return the @code{<derivation>} object of @var{package} cross-built from
@var{system} to @var{target}.
@var{target} must be a valid GNU triplet denoting the target hardware
and operating system, such as @code{"mips64el-linux-gnu"}
(@pxref{Configuration Names, GNU configuration triplets,, configure, GNU
Configure and Build System}).
@end deffn
@node Build Systems
@section Build Systems
@cindex build system
Each package definition specifies a @dfn{build system} and arguments for
that build system (@pxref{Defining Packages}). This @code{build-system}
field represents the build procedure of the package, as well implicit
dependencies of that build procedure.
Build systems are @code{<build-system>} objects. The interface to
create and manipulate them is provided by the @code{(guix build-system)}
module, and actual build systems are exported by specific modules.
@cindex bag (low-level package representation)
Under the hood, build systems first compile package objects to
@dfn{bags}. A @dfn{bag} is like a package, but with less
ornamentation---in other words, a bag is a lower-level representation of
a package, which includes all the inputs of that package, including some
that were implicitly added by the build system. This intermediate
representation is then compiled to a derivation (@pxref{Derivations}).
Build systems accept an optional list of @dfn{arguments}. In package
definitions, these are passed @i{via} the @code{arguments} field
(@pxref{Defining Packages}). They are typically keyword arguments
(@pxref{Optional Arguments, keyword arguments in Guile,, guile, GNU
Guile Reference Manual}). The value of these arguments is usually
evaluated in the @dfn{build stratum}---i.e., by a Guile process launched
by the daemon (@pxref{Derivations}).
The main build system is @var{gnu-build-system}, which implements the
standard build procedure for GNU packages and many other packages. It
is provided by the @code{(guix build-system gnu)} module.
@defvr {Scheme Variable} gnu-build-system
@var{gnu-build-system} represents the GNU Build System, and variants
thereof (@pxref{Configuration, configuration and makefile conventions,,
standards, GNU Coding Standards}).
@cindex build phases
In a nutshell, packages using it configured, built, and installed with
the usual @code{./configure && make && make check && make install}
command sequence. In practice, a few additional steps are often needed.
All these steps are split up in separate @dfn{phases},
notably@footnote{Please see the @code{(guix build gnu-build-system)}
modules for more details about the build phases.}:
@table @code
@item unpack
Unpack the source tarball, and change the current directory to the
extracted source tree. If the source is actually a directory, copy it
to the build tree, and enter that directory.
@item patch-source-shebangs
Patch shebangs encountered in source files so they refer to the right
store file names. For instance, this changes @code{#!/bin/sh} to
@code{#!/gnu/store/@dots{}-bash-4.3/bin/sh}.
@item configure
Run the @file{configure} script with a number of default options, such
as @code{--prefix=/gnu/store/@dots{}}, as well as the options specified
by the @code{#:configure-flags} argument.
@item build
Run @code{make} with the list of flags specified with
@code{#:make-flags}. If the @code{#:parallel-builds?} argument is true
(the default), build with @code{make -j}.
@item check
Run @code{make check}, or some other target specified with
@code{#:test-target}, unless @code{#:tests? #f} is passed. If the
@code{#:parallel-tests?} argument is true (the default), run @code{make
check -j}.
@item install
Run @code{make install} with the flags listed in @code{#:make-flags}.
@item patch-shebangs
Patch shebangs on the installed executable files.
@item strip
Strip debugging symbols from ELF files (unless @code{#:strip-binaries?}
is false), copying them to the @code{debug} output when available
(@pxref{Installing Debugging Files}).
@end table
@vindex %standard-phases
The build-side module @code{(guix build gnu-build-system)} defines
@var{%standard-phases} as the default list of build phases.
@var{%standard-phases} is a list of symbol/procedure pairs, where the
procedure implements the actual phase.
The list of phases used for a particular package can be changed with the
@code{#:phases} parameter. For instance, passing:
@example
#:phases (alist-delete 'configure %standard-phases)
@end example
means that all the phases described above will be used, except the
@code{configure} phase.
In addition, this build system ensures that the ``standard'' environment
for GNU packages is available. This includes tools such as GCC, libc,
Coreutils, Bash, Make, Diffutils, grep, and sed (see the @code{(guix
build-system gnu)} module for a complete list.) We call these the
@dfn{implicit inputs} of a package, because package definitions don't
have to mention them.
@end defvr
Other @code{<build-system>} objects are defined to support other
conventions and tools used by free software packages. They inherit most
of @var{gnu-build-system}, and differ mainly in the set of inputs
implicitly added to the build process, and in the list of phases
executed. Some of these build systems are listed below.
@defvr {Scheme Variable} cmake-build-system
This variable is exported by @code{(guix build-system cmake)}. It
implements the build procedure for packages using the
@url{http://www.cmake.org, CMake build tool}.
It automatically adds the @code{cmake} package to the set of inputs.
Which package is used can be specified with the @code{#:cmake}
parameter.
The @code{#:configure-flags} parameter is taken as a list of flags
passed to the @command{cmake} command. The @code{#:build-type}
parameter specifies in abstract terms the flags passed to the compiler;
it defaults to @code{"RelWithDebInfo"} (short for ``release mode with
debugging information''), which roughly means that code is compiled with
@code{-O2 -g}, as is the case for Autoconf-based packages by default.
@end defvr
@defvr {Scheme Variable} glib-or-gtk-build-system
This variable is exported by @code{(guix build-system glib-or-gtk)}. It
is intended for use with packages making use of GLib or GTK+.
This build system adds the following two phases to the ones defined by
@var{gnu-build-system}:
@table @code
@item glib-or-gtk-wrap
The phase @code{glib-or-gtk-wrap} ensures that programs found under
@file{bin/} are able to find GLib's ``schemas'' and
@uref{https://developer.gnome.org/gtk3/stable/gtk-running.html, GTK+
modules}. This is achieved by wrapping the programs in launch scripts
that appropriately set the @code{XDG_DATA_DIRS} and @code{GTK_PATH}
environment variables.
It is possible to exclude specific package outputs from that wrapping
process by listing their names in the
@code{#:glib-or-gtk-wrap-excluded-outputs} parameter. This is useful
when an output is known not to contain any GLib or GTK+ binaries, and
where wrapping would gratuitously add a dependency of that output on
GLib and GTK+.
@item glib-or-gtk-compile-schemas
The phase @code{glib-or-gtk-compile-schemas} makes sure that all GLib's
@uref{https://developer.gnome.org/gio/stable/glib-compile-schemas.html,
GSettings schemas} are compiled. Compilation is performed by the
@command{glib-compile-schemas} program. It is provided by the package
@code{glib:bin} which is automatically imported by the build system.
The @code{glib} package providing @command{glib-compile-schemas} can be
specified with the @code{#:glib} parameter.
@end table
Both phases are executed after the @code{install} phase.
@end defvr
@defvr {Scheme Variable} python-build-system
This variable is exported by @code{(guix build-system python)}. It
implements the more or less standard build procedure used by Python
packages, which consists in running @code{python setup.py build} and
then @code{python setup.py install --prefix=/gnu/store/@dots{}}.
For packages that install stand-alone Python programs under @code{bin/},
it takes care of wrapping these programs so their @code{PYTHONPATH}
environment variable points to all the Python libraries they depend on.
Which Python package is used can be specified with the @code{#:python}
parameter.
@end defvr
@defvr {Scheme Variable} perl-build-system
This variable is exported by @code{(guix build-system perl)}. It
implements the standard build procedure for Perl packages, which
consists in running @code{perl Makefile.PL PREFIX=/gnu/store/@dots{}},
followed by @code{make} and @code{make install}.
The initial @code{perl Makefile.PL} invocation passes flags specified by
the @code{#:make-maker-flags} parameter.
Which Perl package is used can be specified with @code{#:perl}.
@end defvr
@defvr {Scheme Variable} ruby-build-system
This variable is exported by @code{(guix build-system ruby)}. It
implements the RubyGems build procedure used by Ruby packages, which
involves running @code{gem build} followed by @code{gem install}.
Which Ruby package is used can be specified with the @code{#:ruby}
parameter.
@end defvr
@defvr {Scheme Variable} waf-build-system
This variable is exported by @code{(guix build-system waf)}. It
implements a build procedure around the @code{waf} script. The common
phases---@code{configure}, @code{build}, and @code{install}---are
implemented by passing their names as arguments to the @code{waf}
script.
The @code{waf} script is executed by the Python interpreter. Which
Python package is used to run the script can be specified with the
@code{#:python} parameter.
@end defvr
Lastly, for packages that do not need anything as sophisticated, a
``trivial'' build system is provided. It is trivial in the sense that
it provides basically no support: it does not pull any implicit inputs,
and does not have a notion of build phases.
@defvr {Scheme Variable} trivial-build-system
This variable is exported by @code{(guix build-system trivial)}.
This build system requires a @code{#:builder} argument. This argument
must be a Scheme expression that builds the package's output(s)---as
with @code{build-expression->derivation} (@pxref{Derivations,
@code{build-expression->derivation}}).
@end defvr
@node The Store
@section The Store
@cindex store
@cindex store paths
Conceptually, the @dfn{store} is where derivations that have been
successfully built are stored---by default, under @file{/gnu/store}.
Sub-directories in the store are referred to as @dfn{store paths}. The
store has an associated database that contains information such has the
store paths referred to by each store path, and the list of @emph{valid}
store paths---paths that result from a successful build.
The store is always accessed by the daemon on behalf of its clients
(@pxref{Invoking guix-daemon}). To manipulate the store, clients
connect to the daemon over a Unix-domain socket, send it requests, and
read the result---these are remote procedure calls, or RPCs.
The @code{(guix store)} module provides procedures to connect to the
daemon, and to perform RPCs. These are described below.
@deffn {Scheme Procedure} open-connection [@var{file}] [#:reserve-space? #t]
Connect to the daemon over the Unix-domain socket at @var{file}. When
@var{reserve-space?} is true, instruct it to reserve a little bit of
extra space on the file system so that the garbage collector can still
operate, should the disk become full. Return a server object.
@var{file} defaults to @var{%default-socket-path}, which is the normal
location given the options that were passed to @command{configure}.
@end deffn
@deffn {Scheme Procedure} close-connection @var{server}
Close the connection to @var{server}.
@end deffn
@defvr {Scheme Variable} current-build-output-port
This variable is bound to a SRFI-39 parameter, which refers to the port
where build and error logs sent by the daemon should be written.
@end defvr
Procedures that make RPCs all take a server object as their first
argument.
@deffn {Scheme Procedure} valid-path? @var{server} @var{path}
Return @code{#t} when @var{path} is a valid store path.
@end deffn
@deffn {Scheme Procedure} add-text-to-store @var{server} @var{name} @var{text} [@var{references}]
Add @var{text} under file @var{name} in the store, and return its store
path. @var{references} is the list of store paths referred to by the
resulting store path.
@end deffn
@deffn {Scheme Procedure} build-derivations @var{server} @var{derivations}
Build @var{derivations} (a list of @code{<derivation>} objects or
derivation paths), and return when the worker is done building them.
Return @code{#t} on success.
@end deffn
Note that the @code{(guix monads)} module provides a monad as well as
monadic versions of the above procedures, with the goal of making it
more convenient to work with code that accesses the store (@pxref{The
Store Monad}).
@c FIXME
@i{This section is currently incomplete.}
@node Derivations
@section Derivations
@cindex derivations
Low-level build actions and the environment in which they are performed
are represented by @dfn{derivations}. A derivation contain the
following pieces of information:
@itemize
@item
The outputs of the derivation---derivations produce at least one file or
directory in the store, but may produce more.
@item
The inputs of the derivations, which may be other derivations or plain
files in the store (patches, build scripts, etc.)
@item
The system type targeted by the derivation---e.g., @code{x86_64-linux}.
@item
The file name of a build script in the store, along with the arguments
to be passed.
@item
A list of environment variables to be defined.
@end itemize
@cindex derivation path
Derivations allow clients of the daemon to communicate build actions to
the store. They exist in two forms: as an in-memory representation,
both on the client- and daemon-side, and as files in the store whose
name end in @code{.drv}---these files are referred to as @dfn{derivation
paths}. Derivations paths can be passed to the @code{build-derivations}
procedure to perform the build actions they prescribe (@pxref{The
Store}).
The @code{(guix derivations)} module provides a representation of
derivations as Scheme objects, along with procedures to create and
otherwise manipulate derivations. The lowest-level primitive to create
a derivation is the @code{derivation} procedure:
@deffn {Scheme Procedure} derivation @var{store} @var{name} @var{builder} @
@var{args} [#:outputs '("out")] [#:hash #f] [#:hash-algo #f] @
[#:recursive? #f] [#:inputs '()] [#:env-vars '()] @
[#:system (%current-system)] [#:references-graphs #f] @
[#:allowed-references #f] [#:local-build? #f]
Build a derivation with the given arguments, and return the resulting
@code{<derivation>} object.
When @var{hash} and @var{hash-algo} are given, a
@dfn{fixed-output derivation} is created---i.e., one whose result is
known in advance, such as a file download. If, in addition,
@var{recursive?} is true, then that fixed output may be an executable
file or a directory and @var{hash} must be the hash of an archive
containing this output.
When @var{references-graphs} is true, it must be a list of file
name/store path pairs. In that case, the reference graph of each store
path is exported in the build environment in the corresponding file, in
a simple text format.
When @var{allowed-references} is true, it must be a list of store items
or outputs that the derivation's output may refer to.
When @var{local-build?} is true, declare that the derivation is not a
good candidate for offloading and should rather be built locally
(@pxref{Daemon Offload Setup}). This is the case for small derivations
where the costs of data transfers would outweigh the benefits.
@end deffn
@noindent
Here's an example with a shell script as its builder, assuming
@var{store} is an open connection to the daemon, and @var{bash} points
to a Bash executable in the store:
@lisp
(use-modules (guix utils)
(guix store)
(guix derivations))
(let ((builder ; add the Bash script to the store
(add-text-to-store store "my-builder.sh"
"echo hello world > $out\n" '())))
(derivation store "foo"
bash `("-e" ,builder)
#:inputs `((,bash) (,builder))
#:env-vars '(("HOME" . "/homeless"))))
@result{} #<derivation /gnu/store/@dots{}-foo.drv => /gnu/store/@dots{}-foo>
@end lisp
As can be guessed, this primitive is cumbersome to use directly. A
better approach is to write build scripts in Scheme, of course! The
best course of action for that is to write the build code as a
``G-expression'', and to pass it to @code{gexp->derivation}. For more
information, @pxref{G-Expressions}.
Once upon a time, @code{gexp->derivation} did not exist and constructing
derivations with build code written in Scheme was achieved with
@code{build-expression->derivation}, documented below. This procedure
is now deprecated in favor of the much nicer @code{gexp->derivation}.
@deffn {Scheme Procedure} build-expression->derivation @var{store} @
@var{name} @var{exp} @
[#:system (%current-system)] [#:inputs '()] @
[#:outputs '("out")] [#:hash #f] [#:hash-algo #f] @
[#:recursive? #f] [#:env-vars '()] [#:modules '()] @
[#:references-graphs #f] [#:allowed-references #f] @
[#:local-build? #f] [#:guile-for-build #f]
Return a derivation that executes Scheme expression @var{exp} as a
builder for derivation @var{name}. @var{inputs} must be a list of
@code{(name drv-path sub-drv)} tuples; when @var{sub-drv} is omitted,
@code{"out"} is assumed. @var{modules} is a list of names of Guile
modules from the current search path to be copied in the store,
compiled, and made available in the load path during the execution of
@var{exp}---e.g., @code{((guix build utils) (guix build
gnu-build-system))}.
@var{exp} is evaluated in an environment where @code{%outputs} is bound
to a list of output/path pairs, and where @code{%build-inputs} is bound
to a list of string/output-path pairs made from @var{inputs}.
Optionally, @var{env-vars} is a list of string pairs specifying the name
and value of environment variables visible to the builder. The builder
terminates by passing the result of @var{exp} to @code{exit}; thus, when
@var{exp} returns @code{#f}, the build is considered to have failed.
@var{exp} is built using @var{guile-for-build} (a derivation). When
@var{guile-for-build} is omitted or is @code{#f}, the value of the
@code{%guile-for-build} fluid is used instead.
See the @code{derivation} procedure for the meaning of
@var{references-graphs}, @var{allowed-references}, and @var{local-build?}.
@end deffn
@noindent
Here's an example of a single-output derivation that creates a directory
containing one file:
@lisp
(let ((builder '(let ((out (assoc-ref %outputs "out")))
(mkdir out) ; create /gnu/store/@dots{}-goo
(call-with-output-file (string-append out "/test")
(lambda (p)
(display '(hello guix) p))))))
(build-expression->derivation store "goo" builder))
@result{} #<derivation /gnu/store/@dots{}-goo.drv => @dots{}>
@end lisp
@node The Store Monad
@section The Store Monad
@cindex monad
The procedures that operate on the store described in the previous
sections all take an open connection to the build daemon as their first
argument. Although the underlying model is functional, they either have
side effects or depend on the current state of the store.
The former is inconvenient: the connection to the build daemon has to be
carried around in all those functions, making it impossible to compose
functions that do not take that parameter with functions that do. The
latter can be problematic: since store operations have side effects
and/or depend on external state, they have to be properly sequenced.
@cindex monadic values
@cindex monadic functions
This is where the @code{(guix monads)} module comes in. This module
provides a framework for working with @dfn{monads}, and a particularly
useful monad for our uses, the @dfn{store monad}. Monads are a
construct that allows two things: associating ``context'' with values
(in our case, the context is the store), and building sequences of
computations (here computations include accesses to the store.) Values
in a monad---values that carry this additional context---are called
@dfn{monadic values}; procedures that return such values are called
@dfn{monadic procedures}.
Consider this ``normal'' procedure:
@example
(define (sh-symlink store)
;; Return a derivation that symlinks the 'bash' executable.
(let* ((drv (package-derivation store bash))
(out (derivation->output-path drv))
(sh (string-append out "/bin/bash")))
(build-expression->derivation store "sh"
`(symlink ,sh %output))))
@end example
Using @code{(guix monads)}, it may be rewritten as a monadic function:
@c FIXME: Find a better example, one that uses 'mlet'.
@example
(define (sh-symlink)
;; Same, but return a monadic value.
(gexp->derivation "sh"
#~(symlink (string-append #$bash "/bin/bash") #$output)))
@end example
There are two things to note in the second version: the @code{store}
parameter is now implicit, and the monadic value returned by
@code{package-file}---a wrapper around @code{package-derivation} and
@code{derivation->output-path}---is @dfn{bound} using @code{mlet}
instead of plain @code{let}.
Calling the monadic @code{profile.sh} has no effect. To get the desired
effect, one must use @code{run-with-store}:
@example
(run-with-store (open-connection) (profile.sh))
@result{} /gnu/store/...-profile.sh
@end example
Note that the @code{(guix monad-repl)} module extends Guile's REPL with
new ``meta-commands'' to make it easier to deal with monadic procedures:
@code{run-in-store}, and @code{enter-store-monad}. The former, is used
to ``run'' a single monadic value through the store:
@example
scheme@@(guile-user)> ,run-in-store (package->derivation hello)
$1 = #<derivation /gnu/store/@dots{}-hello-2.9.drv => @dots{}>
@end example
The latter enters a recursive REPL, where all the return values are
automatically run through the store:
@example
scheme@@(guile-user)> ,enter-store-monad
store-monad@@(guile-user) [1]> (package->derivation hello)
$2 = #<derivation /gnu/store/@dots{}-hello-2.9.drv => @dots{}>
store-monad@@(guile-user) [1]> (text-file "foo" "Hello!")
$3 = "/gnu/store/@dots{}-foo"
store-monad@@(guile-user) [1]> ,q
scheme@@(guile-user)>
@end example
@noindent
Note that non-monadic values cannot be returned in the
@code{store-monad} REPL.
The main syntactic forms to deal with monads in general are provided by
the @code{(guix monads)} module and are described below.
@deffn {Scheme Syntax} with-monad @var{monad} @var{body} ...
Evaluate any @code{>>=} or @code{return} forms in @var{body} as being
in @var{monad}.
@end deffn
@deffn {Scheme Syntax} return @var{val}
Return a monadic value that encapsulates @var{val}.
@end deffn
@deffn {Scheme Syntax} >>= @var{mval} @var{mproc}
@dfn{Bind} monadic value @var{mval}, passing its ``contents'' to monadic
procedure @var{mproc}@footnote{This operation is commonly referred to as
``bind'', but that name denotes an unrelated procedure in Guile. Thus
we use this somewhat cryptic symbol inherited from the Haskell
language.}.
@end deffn
@deffn {Scheme Syntax} mlet @var{monad} ((@var{var} @var{mval}) ...) @
@var{body} ...
@deffnx {Scheme Syntax} mlet* @var{monad} ((@var{var} @var{mval}) ...) @
@var{body} ...
Bind the variables @var{var} to the monadic values @var{mval} in
@var{body}. The form (@var{var} -> @var{val}) binds @var{var} to the
``normal'' value @var{val}, as per @code{let}.
@code{mlet*} is to @code{mlet} what @code{let*} is to @code{let}
(@pxref{Local Bindings,,, guile, GNU Guile Reference Manual}).
@end deffn
@deffn {Scheme System} mbegin @var{monad} @var{mexp} ...
Bind @var{mexp} and the following monadic expressions in sequence,
returning the result of the last expression.
This is akin to @code{mlet}, except that the return values of the
monadic expressions are ignored. In that sense, it is analogous to
@code{begin}, but applied to monadic expressions.
@end deffn
@cindex state monad
The @code{(guix monads)} module provides the @dfn{state monad}, which
allows an additional value---the state---to be @emph{threaded} through
monadic procedure calls.
@defvr {Scheme Variable} %state-monad
The state monad. Procedures in the state monad can access and change
the state that is threaded.
Consider the example below. The @code{square} procedure returns a value
in the state monad. It returns the square of its argument, but also
increments the current state value:
@example
(define (square x)
(mlet %state-monad ((count (current-state)))
(mbegin %state-monad
(set-current-state (+ 1 count))
(return (* x x)))))
(run-with-state (sequence %state-monad (map square (iota 3))) 0)
@result{} (0 1 4)
@result{} 3
@end example
When ``run'' through @var{%state-monad}, we obtain that additional state
value, which is the number of @code{square} calls.
@end defvr
@deffn {Monadic Procedure} current-state
Return the current state as a monadic value.
@end deffn
@deffn {Monadic Procedure} set-current-state @var{value}
Set the current state to @var{value} and return the previous state as a
monadic value.
@end deffn
@deffn {Monadic Procedure} state-push @var{value}
Push @var{value} to the current state, which is assumed to be a list,
and return the previous state as a monadic value.
@end deffn
@deffn {Monadic Procedure} state-pop
Pop a value from the current state and return it as a monadic value.
The state is assumed to be a list.
@end deffn
@deffn {Scheme Procedure} run-with-state @var{mval} [@var{state}]
Run monadic value @var{mval} starting with @var{state} as the initial
state. Return two values: the resulting value, and the resulting state.
@end deffn
The main interface to the store monad, provided by the @code{(guix
store)} module, is as follows.
@defvr {Scheme Variable} %store-monad
The store monad---an alias for @var{%state-monad}.
Values in the store monad encapsulate accesses to the store. When its
effect is needed, a value of the store monad must be ``evaluated'' by
passing it to the @code{run-with-store} procedure (see below.)
@end defvr
@deffn {Scheme Procedure} run-with-store @var{store} @var{mval} [#:guile-for-build] [#:system (%current-system)]
Run @var{mval}, a monadic value in the store monad, in @var{store}, an
open store connection.
@end deffn
@deffn {Monadic Procedure} text-file @var{name} @var{text}
Return as a monadic value the absolute file name in the store of the file
containing @var{text}, a string.
@end deffn
@deffn {Monadic Procedure} interned-file @var{file} [@var{name}] @
[#:recursive? #t]
Return the name of @var{file} once interned in the store. Use
@var{name} as its store name, or the basename of @var{file} if
@var{name} is omitted.
When @var{recursive?} is true, the contents of @var{file} are added
recursively; if @var{file} designates a flat file and @var{recursive?}
is true, its contents are added, and its permission bits are kept.
The example below adds a file to the store, under two different names:
@example
(run-with-store (open-connection)
(mlet %store-monad ((a (interned-file "README"))
(b (interned-file "README" "LEGU-MIN")))
(return (list a b))))
@result{} ("/gnu/store/rwm@dots{}-README" "/gnu/store/44i@dots{}-LEGU-MIN")
@end example
@end deffn
The @code{(guix packages)} module exports the following package-related
monadic procedures:
@deffn {Monadic Procedure} package-file @var{package} [@var{file}] @
[#:system (%current-system)] [#:target #f] @
[#:output "out"] Return as a monadic
value in the absolute file name of @var{file} within the @var{output}
directory of @var{package}. When @var{file} is omitted, return the name
of the @var{output} directory of @var{package}. When @var{target} is
true, use it as a cross-compilation target triplet.
@end deffn
@deffn {Monadic Procedure} package->derivation @var{package} [@var{system}]
@deffnx {Monadic Procedure} package->cross-derivation @var{package} @
@var{target} [@var{system}]
Monadic version of @code{package-derivation} and
@code{package-cross-derivation} (@pxref{Defining Packages}).
@end deffn
@node G-Expressions
@section G-Expressions
@cindex G-expression
@cindex build code quoting
So we have ``derivations'', which represent a sequence of build actions
to be performed to produce an item in the store (@pxref{Derivations}).
Those build actions are performed when asking the daemon to actually
build the derivations; they are run by the daemon in a container
(@pxref{Invoking guix-daemon}).
@cindex strata of code
It should come as no surprise that we like to write those build actions
in Scheme. When we do that, we end up with two @dfn{strata} of Scheme
code@footnote{The term @dfn{stratum} in this context was coined by
Manuel Serrano et al.@: in the context of their work on Hop. Oleg
Kiselyov, who has written insightful
@url{http://okmij.org/ftp/meta-programming/#meta-scheme, essays and code
on this topic}, refers to this kind of code generation as
@dfn{staging}.}: the ``host code''---code that defines packages, talks
to the daemon, etc.---and the ``build code''---code that actually
performs build actions, such as making directories, invoking
@command{make}, etc.
To describe a derivation and its build actions, one typically needs to
embed build code inside host code. It boils down to manipulating build
code as data, and Scheme's homoiconicity---code has a direct
representation as data---comes in handy for that. But we need more than
Scheme's normal @code{quasiquote} mechanism to construct build
expressions.
The @code{(guix gexp)} module implements @dfn{G-expressions}, a form of
S-expressions adapted to build expressions. G-expressions, or
@dfn{gexps}, consist essentially in three syntactic forms: @code{gexp},
@code{ungexp}, and @code{ungexp-splicing} (or simply: @code{#~},
@code{#$}, and @code{#$@@}), which are comparable respectively to
@code{quasiquote}, @code{unquote}, and @code{unquote-splicing}
(@pxref{Expression Syntax, @code{quasiquote},, guile, GNU Guile
Reference Manual}). However, there are major differences:
@itemize
@item
Gexps are meant to be written to a file and run or manipulated by other
processes.
@item
When a package or derivation is unquoted inside a gexp, the result is as
if its output file name had been introduced.
@item
Gexps carry information about the packages or derivations they refer to,
and these dependencies are automatically added as inputs to the build
processes that use them.
@end itemize
To illustrate the idea, here is an example of a gexp:
@example
(define build-exp
#~(begin
(mkdir #$output)
(chdir #$output)
(symlink (string-append #$coreutils "/bin/ls")
"list-files")))
@end example
This gexp can be passed to @code{gexp->derivation}; we obtain a
derivation that builds a directory containing exactly one symlink to
@file{/gnu/store/@dots{}-coreutils-8.22/bin/ls}:
@example
(gexp->derivation "the-thing" build-exp)
@end example
As one would expect, the @code{"/gnu/store/@dots{}-coreutils-8.22"} string is
substituted to the reference to the @var{coreutils} package in the
actual build code, and @var{coreutils} is automatically made an input to
the derivation. Likewise, @code{#$output} (equivalent to @code{(ungexp
output)}) is replaced by a string containing the derivation's output
directory name.
@cindex cross compilation
In a cross-compilation context, it is useful to distinguish between
references to the @emph{native} build of a package---that can run on the
host---versus references to cross builds of a package. To that end, the
@code{#+} plays the same role as @code{#$}, but is a reference to a
native package build:
@example
(gexp->derivation "vi"
#~(begin
(mkdir #$output)
(system* (string-append #+coreutils "/bin/ln")
"-s"
(string-append #$emacs "/bin/emacs")
(string-append #$output "/bin/vi")))
#:target "mips64el-linux")
@end example
@noindent
In the example above, the native build of @var{coreutils} is used, so
that @command{ln} can actually run on the host; but then the
cross-compiled build of @var{emacs} is referenced.
The syntactic form to construct gexps is summarized below.
@deffn {Scheme Syntax} #~@var{exp}
@deffnx {Scheme Syntax} (gexp @var{exp})
Return a G-expression containing @var{exp}. @var{exp} may contain one
or more of the following forms:
@table @code
@item #$@var{obj}
@itemx (ungexp @var{obj})
Introduce a reference to @var{obj}. @var{obj} may be a package or a
derivation, in which case the @code{ungexp} form is replaced by its
output file name---e.g., @code{"/gnu/store/@dots{}-coreutils-8.22}.
If @var{obj} is a list, it is traversed and any package or derivation
references are substituted similarly.
If @var{obj} is another gexp, its contents are inserted and its
dependencies are added to those of the containing gexp.
If @var{obj} is another kind of object, it is inserted as is.
@item #$@var{package-or-derivation}:@var{output}
@itemx (ungexp @var{package-or-derivation} @var{output})
This is like the form above, but referring explicitly to the
@var{output} of @var{package-or-derivation}---this is useful when
@var{package-or-derivation} produces multiple outputs (@pxref{Packages
with Multiple Outputs}).
@item #+@var{obj}
@itemx #+@var{obj}:output
@itemx (ungexp-native @var{obj})
@itemx (ungexp-native @var{obj} @var{output})
Same as @code{ungexp}, but produces a reference to the @emph{native}
build of @var{obj} when used in a cross compilation context.
@item #$output[:@var{output}]
@itemx (ungexp output [@var{output}])
Insert a reference to derivation output @var{output}, or to the main
output when @var{output} is omitted.
This only makes sense for gexps passed to @code{gexp->derivation}.
@item #$@@@var{lst}
@itemx (ungexp-splicing @var{lst})
Like the above, but splices the contents of @var{lst} inside the
containing list.
@item #+@@@var{lst}
@itemx (ungexp-native-splicing @var{lst})
Like the above, but refers to native builds of the objects listed in
@var{lst}.
@end table
G-expressions created by @code{gexp} or @code{#~} are run-time objects
of the @code{gexp?} type (see below.)
@end deffn
@deffn {Scheme Procedure} gexp? @var{obj}
Return @code{#t} if @var{obj} is a G-expression.
@end deffn
G-expressions are meant to be written to disk, either as code building
some derivation, or as plain files in the store. The monadic procedures
below allow you to do that (@pxref{The Store Monad}, for more
information about monads.)
@deffn {Monadic Procedure} gexp->derivation @var{name} @var{exp} @
[#:system (%current-system)] [#:target #f] [#:inputs '()] @
[#:hash #f] [#:hash-algo #f] @
[#:recursive? #f] [#:env-vars '()] [#:modules '()] @
[#:module-path @var{%load-path}] @
[#:references-graphs #f] [#:local-build? #f] @
[#:guile-for-build #f]
Return a derivation @var{name} that runs @var{exp} (a gexp) with
@var{guile-for-build} (a derivation) on @var{system}. When @var{target}
is true, it is used as the cross-compilation target triplet for packages
referred to by @var{exp}.
Make @var{modules} available in the evaluation context of @var{EXP};
@var{MODULES} is a list of names of Guile modules searched in
@var{MODULE-PATH} to be copied in the store, compiled, and made available in
the load path during the execution of @var{exp}---e.g., @code{((guix
build utils) (guix build gnu-build-system))}.
When @var{references-graphs} is true, it must be a list of tuples of one of the
following forms:
@example
(@var{file-name} @var{package})
(@var{file-name} @var{package} @var{output})
(@var{file-name} @var{derivation})
(@var{file-name} @var{derivation} @var{output})
(@var{file-name} @var{store-item})
@end example
The right-hand-side of each element of @var{references-graphs} is automatically made
an input of the build process of @var{exp}. In the build environment, each
@var{file-name} contains the reference graph of the corresponding item, in a simple
text format.
The other arguments are as for @code{derivation} (@pxref{Derivations}).
@end deffn
@deffn {Monadic Procedure} gexp->script @var{name} @var{exp}
Return an executable script @var{name} that runs @var{exp} using
@var{guile} with @var{modules} in its search path.
The example below builds a script that simply invokes the @command{ls}
command:
@example
(use-modules (guix gexp) (gnu packages base))
(gexp->script "list-files"
#~(execl (string-append #$coreutils "/bin/ls")
"ls"))
@end example
When ``running'' it through the store (@pxref{The Store Monad,
@code{run-with-store}}), we obtain a derivation that produces an
executable file @file{/gnu/store/@dots{}-list-files} along these lines:
@example
#!/gnu/store/@dots{}-guile-2.0.11/bin/guile -ds
!#
(execl (string-append "/gnu/store/@dots{}-coreutils-8.22"/bin/ls")
"ls")
@end example
@end deffn
@deffn {Monadic Procedure} gexp->file @var{name} @var{exp}
Return a derivation that builds a file @var{name} containing @var{exp}.
The resulting file holds references to all the dependencies of @var{exp}
or a subset thereof.
@end deffn
@deffn {Monadic Procedure} text-file* @var{name} @var{text} @dots{}
Return as a monadic value a derivation that builds a text file
containing all of @var{text}. @var{text} may list, in addition to
strings, packages, derivations, and store file names; the resulting
store file holds references to all these.
This variant should be preferred over @code{text-file} anytime the file
to create will reference items from the store. This is typically the
case when building a configuration file that embeds store file names,
like this:
@example
(define (profile.sh)
;; Return the name of a shell script in the store that
;; initializes the 'PATH' environment variable.
(text-file* "profile.sh"
"export PATH=" coreutils "/bin:"
grep "/bin:" sed "/bin\n"))
@end example
In this example, the resulting @file{/gnu/store/@dots{}-profile.sh} file
will references @var{coreutils}, @var{grep}, and @var{sed}, thereby
preventing them from being garbage-collected during its lifetime.
@end deffn
Of course, in addition to gexps embedded in ``host'' code, there are
also modules containing build tools. To make it clear that they are
meant to be used in the build stratum, these modules are kept in the
@code{(guix build @dots{})} name space.
@c *********************************************************************
@node Utilities
@chapter Utilities
This section describes tools primarily targeted at developers and users
who write new package definitions. They complement the Scheme
programming interface of Guix in a convenient way.
@menu
* Invoking guix build:: Building packages from the command line.
* Invoking guix download:: Downloading a file and printing its hash.
* Invoking guix hash:: Computing the cryptographic hash of a file.
* Invoking guix import:: Importing package definitions.
* Invoking guix refresh:: Updating package definitions.
* Invoking guix lint:: Finding errors in package definitions.
* Invoking guix environment:: Setting up development environments.
@end menu
@node Invoking guix build
@section Invoking @command{guix build}
The @command{guix build} command builds packages or derivations and
their dependencies, and prints the resulting store paths. Note that it
does not modify the user's profile---this is the job of the
@command{guix package} command (@pxref{Invoking guix package}). Thus,
it is mainly useful for distribution developers.
The general syntax is:
@example
guix build @var{options} @var{package-or-derivation}@dots{}
@end example
@var{package-or-derivation} may be either the name of a package found in
the software distribution such as @code{coreutils} or
@code{coreutils-8.20}, or a derivation such as
@file{/gnu/store/@dots{}-coreutils-8.19.drv}. In the former case, a
package with the corresponding name (and optionally version) is searched
for among the GNU distribution modules (@pxref{Package Modules}).
Alternatively, the @code{--expression} option may be used to specify a
Scheme expression that evaluates to a package; this is useful when
disambiguation among several same-named packages or package variants is
needed.
The @var{options} may be zero or more of the following:
@table @code
@item --expression=@var{expr}
@itemx -e @var{expr}
Build the package or derivation @var{expr} evaluates to.
For example, @var{expr} may be @code{(@@ (gnu packages guile)
guile-1.8)}, which unambiguously designates this specific variant of
version 1.8 of Guile.
Alternately, @var{expr} may be a G-expression, in which case it is used
as a build program passed to @code{gexp->derivation}
(@pxref{G-Expressions}).
Lastly, @var{expr} may refer to a zero-argument monadic procedure
(@pxref{The Store Monad}). The procedure must return a derivation as a
monadic value, which is then passed through @code{run-with-store}.
@item --source
@itemx -S
Build the packages' source derivations, rather than the packages
themselves.
For instance, @code{guix build -S gcc} returns something like
@file{/gnu/store/@dots{}-gcc-4.7.2.tar.bz2}, which is GCC's source tarball.
The returned source tarball is the result of applying any patches and
code snippets specified in the package's @code{origin} (@pxref{Defining
Packages}).
@item --system=@var{system}
@itemx -s @var{system}
Attempt to build for @var{system}---e.g., @code{i686-linux}---instead of
the host's system type.
An example use of this is on Linux-based systems, which can emulate
different personalities. For instance, passing
@code{--system=i686-linux} on an @code{x86_64-linux} system allows users
to build packages in a complete 32-bit environment.
@item --target=@var{triplet}
@cindex cross-compilation
Cross-build for @var{triplet}, which must be a valid GNU triplet, such
as @code{"mips64el-linux-gnu"} (@pxref{Configuration Names, GNU
configuration triplets,, configure, GNU Configure and Build System}).
@item --with-source=@var{source}
Use @var{source} as the source of the corresponding package.
@var{source} must be a file name or a URL, as for @command{guix
download} (@pxref{Invoking guix download}).
The ``corresponding package'' is taken to be one specified on the
command line whose name matches the base of @var{source}---e.g., if
@var{source} is @code{/src/guile-2.0.10.tar.gz}, the corresponding
package is @code{guile}. Likewise, the version string is inferred from
@var{source}; in the previous example, it's @code{2.0.10}.
This option allows users to try out versions of packages other than the
one provided by the distribution. The example below downloads
@file{ed-1.7.tar.gz} from a GNU mirror and uses that as the source for
the @code{ed} package:
@example
guix build ed --with-source=mirror://gnu/ed/ed-1.7.tar.gz
@end example
As a developer, @code{--with-source} makes it easy to test release
candidates:
@example
guix build guile --with-source=../guile-2.0.9.219-e1bb7.tar.xz
@end example
@item --no-grafts
Do not ``graft'' packages. In practice, this means that package updates
available as grafts are not applied. @xref{Security Updates}, for more
information on grafts.
@item --derivations
@itemx -d
Return the derivation paths, not the output paths, of the given
packages.
@item --root=@var{file}
@itemx -r @var{file}
Make @var{file} a symlink to the result, and register it as a garbage
collector root.
@item --log-file
Return the build log file names for the given
@var{package-or-derivation}s, or raise an error if build logs are
missing.
This works regardless of how packages or derivations are specified. For
instance, the following invocations are equivalent:
@example
guix build --log-file `guix build -d guile`
guix build --log-file `guix build guile`
guix build --log-file guile
guix build --log-file -e '(@@ (gnu packages guile) guile-2.0)'
@end example
@end table
@cindex common build options
In addition, a number of options that control the build process are
common to @command{guix build} and other commands that can spawn builds,
such as @command{guix package} or @command{guix archive}. These are the
following:
@table @code
@item --load-path=@var{directory}
@itemx -L @var{directory}
Add @var{directory} to the front of the package module search path
(@pxref{Package Modules}).
This allows users to define their own packages and make them visible to
the command-line tools.
@item --keep-failed
@itemx -K
Keep the build tree of failed builds. Thus, if a build fail, its build
tree is kept under @file{/tmp}, in a directory whose name is shown at
the end of the build log. This is useful when debugging build issues.
@item --dry-run
@itemx -n
Do not build the derivations.
@item --fallback
When substituting a pre-built binary fails, fall back to building
packages locally.
@item --no-substitutes
Do not use substitutes for build products. That is, always build things
locally instead of allowing downloads of pre-built binaries
(@pxref{Substitutes}).
@item --no-build-hook
Do not attempt to offload builds @i{via} the daemon's ``build hook''
(@pxref{Daemon Offload Setup}). That is, always build things locally
instead of offloading builds to remote machines.
@item --max-silent-time=@var{seconds}
When the build or substitution process remains silent for more than
@var{seconds}, terminate it and report a build failure.
@item --timeout=@var{seconds}
Likewise, when the build or substitution process lasts for more than
@var{seconds}, terminate it and report a build failure.
By default there is no timeout. This behavior can be restored with
@code{--timeout=0}.
@item --verbosity=@var{level}
Use the given verbosity level. @var{level} must be an integer between 0
and 5; higher means more verbose output. Setting a level of 4 or more
may be helpful when debugging setup issues with the build daemon.
@item --cores=@var{n}
@itemx -c @var{n}
Allow the use of up to @var{n} CPU cores for the build. The special
value @code{0} means to use as many CPU cores as available.
@item --max-jobs=@var{n}
@itemx -M @var{n}
Allow at most @var{n} build jobs in parallel. @xref{Invoking
guix-daemon, @code{--max-jobs}}, for details about this option and the
equivalent @command{guix-daemon} option.
@end table
Behind the scenes, @command{guix build} is essentially an interface to
the @code{package-derivation} procedure of the @code{(guix packages)}
module, and to the @code{build-derivations} procedure of the @code{(guix
derivations)} module.
In addition to options explicitly passed on the command line,
@command{guix build} and other @command{guix} commands that support
building honor the @code{GUIX_BUILD_OPTIONS} environment variable.
@defvr {Environment Variable} GUIX_BUILD_OPTIONS
Users can define this variable to a list of command line options that
will automatically be used by @command{guix build} and other
@command{guix} commands that can perform builds, as in the example
below:
@example
$ export GUIX_BUILD_OPTIONS="--no-substitutes -c 2 -L /foo/bar"
@end example
These options are parsed independently, and the result is appended to
the parsed command-line options.
@end defvr
@node Invoking guix download
@section Invoking @command{guix download}
When writing a package definition, developers typically need to download
the package's source tarball, compute its SHA256 hash, and write that
hash in the package definition (@pxref{Defining Packages}). The
@command{guix download} tool helps with this task: it downloads a file
from the given URI, adds it to the store, and prints both its file name
in the store and its SHA256 hash.
The fact that the downloaded file is added to the store saves bandwidth:
when the developer eventually tries to build the newly defined package
with @command{guix build}, the source tarball will not have to be
downloaded again because it is already in the store. It is also a
convenient way to temporarily stash files, which may be deleted
eventually (@pxref{Invoking guix gc}).
The @command{guix download} command supports the same URIs as used in
package definitions. In particular, it supports @code{mirror://} URIs.
@code{https} URIs (HTTP over TLS) are supported @emph{provided} the
Guile bindings for GnuTLS are available in the user's environment; when
they are not available, an error is raised. @xref{Guile Preparations,
how to install the GnuTLS bindings for Guile,, gnutls-guile,
GnuTLS-Guile}, for more information.
The following option is available:
@table @code
@item --format=@var{fmt}
@itemx -f @var{fmt}
Write the hash in the format specified by @var{fmt}. For more
information on the valid values for @var{fmt}, @pxref{Invoking guix hash}.
@end table
@node Invoking guix hash
@section Invoking @command{guix hash}
The @command{guix hash} command computes the SHA256 hash of a file.
It is primarily a convenience tool for anyone contributing to the
distribution: it computes the cryptographic hash of a file, which can be
used in the definition of a package (@pxref{Defining Packages}).
The general syntax is:
@example
guix hash @var{option} @var{file}
@end example
@command{guix hash} has the following option:
@table @code
@item --format=@var{fmt}
@itemx -f @var{fmt}
Write the hash in the format specified by @var{fmt}.
Supported formats: @code{nix-base32}, @code{base32}, @code{base16}
(@code{hex} and @code{hexadecimal} can be used as well).
If the @option{--format} option is not specified, @command{guix hash}
will output the hash in @code{nix-base32}. This representation is used
in the definitions of packages.
@item --recursive
@itemx -r
Compute the hash on @var{file} recursively.
In this case, the hash is computed on an archive containing @var{file},
including its children if it is a directory. Some of @var{file}'s
meta-data is part of the archive; for instance, when @var{file} is a
regular file, the hash is different depending on whether @var{file} is
executable or not. Meta-data such as time stamps has no impact on the
hash (@pxref{Invoking guix archive}).
@c FIXME: Replace xref above with xref to an ``Archive'' section when
@c it exists.
@end table
@node Invoking guix import
@section Invoking @command{guix import}
@cindex importing packages
@cindex package import
@cindex package conversion
The @command{guix import} command is useful for people willing to add a
package to the distribution but who'd rather do as little work as
possible to get there---a legitimate demand. The command knows of a few
repositories from which it can ``import'' package meta-data. The result
is a package definition, or a template thereof, in the format we know
(@pxref{Defining Packages}).
The general syntax is:
@example
guix import @var{importer} @var{options}@dots{}
@end example
@var{importer} specifies the source from which to import package
meta-data, and @var{options} specifies a package identifier and other
options specific to @var{importer}. Currently, the available
``importers'' are:
@table @code
@item gnu
Import meta-data for the given GNU package. This provides a template
for the latest version of that GNU package, including the hash of its
source tarball, and its canonical synopsis and description.
Additional information such as the package's dependencies and its
license needs to be figured out manually.
For example, the following command returns a package definition for
GNU@tie{}Hello:
@example
guix import gnu hello
@end example
Specific command-line options are:
@table @code
@item --key-download=@var{policy}
As for @code{guix refresh}, specify the policy to handle missing OpenPGP
keys when verifying the package's signature. @xref{Invoking guix
refresh, @code{--key-download}}.
@end table
@item pypi
@cindex pypi
Import meta-data from the @uref{https://pypi.python.org/, Python Package
Index}@footnote{This functionality requires Guile-JSON to be installed.
@xref{Requirements}.}. Information is taken from the JSON-formatted
description available at @code{pypi.python.org} and usually includes all
the relevant information, including package dependencies.
The command below imports meta-data for the @code{itsdangerous} Python
package:
@example
guix import pypi itsdangerous
@end example
@item cpan
@cindex CPAN
Import meta-data from @uref{https://www.metacpan.org/, MetaCPAN}.
Information is taken from the JSON-formatted meta-data provided through
@uref{https://api.metacpan.org/, MetaCPAN's API} and includes most
relevant information. License information should be checked closely.
Package dependencies are included but may in some cases needlessly
include core Perl modules.
The command command below imports meta-data for the @code{Acme::Boolean}
Perl module:
@example
guix import cpan Acme::Boolean
@end example
@item nix
Import meta-data from a local copy of the source of the
@uref{http://nixos.org/nixpkgs/, Nixpkgs distribution}@footnote{This
relies on the @command{nix-instantiate} command of
@uref{http://nixos.org/nix/, Nix}.}. Package definitions in Nixpkgs are
typically written in a mixture of Nix-language and Bash code. This
command only imports the high-level package structure that is written in
the Nix language. It normally includes all the basic fields of a
package definition.
When importing a GNU package, the synopsis and descriptions are replaced
by their canonical upstream variant.
As an example, the command below imports the package definition of
LibreOffice (more precisely, it imports the definition of the package
bound to the @code{libreoffice} top-level attribute):
@example
guix import nix ~/path/to/nixpkgs libreoffice
@end example
@end table
The structure of the @command{guix import} code is modular. It would be
useful to have more importers for other package formats, and your help
is welcome here (@pxref{Contributing}).
@node Invoking guix refresh
@section Invoking @command{guix refresh}
The primary audience of the @command{guix refresh} command is developers
of the GNU software distribution. By default, it reports any packages
provided by the distribution that are outdated compared to the latest
upstream version, like this:
@example
$ guix refresh
gnu/packages/gettext.scm:29:13: gettext would be upgraded from 0.18.1.1 to 0.18.2.1
gnu/packages/glib.scm:77:12: glib would be upgraded from 2.34.3 to 2.37.0
@end example
It does so by browsing each package's FTP directory and determining the
highest version number of the source tarballs
therein@footnote{Currently, this only works for GNU packages.}.
When passed @code{--update}, it modifies distribution source files to
update the version numbers and source tarball hashes of those packages'
recipes (@pxref{Defining Packages}). This is achieved by downloading
each package's latest source tarball and its associated OpenPGP
signature, authenticating the downloaded tarball against its signature
using @command{gpg}, and finally computing its hash. When the public
key used to sign the tarball is missing from the user's keyring, an
attempt is made to automatically retrieve it from a public key server;
when it's successful, the key is added to the user's keyring; otherwise,
@command{guix refresh} reports an error.
The following options are supported:
@table @code
@item --update
@itemx -u
Update distribution source files (package recipes) in place.
@xref{Defining Packages}, for more information on package definitions.
@item --select=[@var{subset}]
@itemx -s @var{subset}
Select all the packages in @var{subset}, one of @code{core} or
@code{non-core}.
The @code{core} subset refers to all the packages at the core of the
distribution---i.e., packages that are used to build ``everything
else''. This includes GCC, libc, Binutils, Bash, etc. Usually,
changing one of these packages in the distribution entails a rebuild of
all the others. Thus, such updates are an inconvenience to users in
terms of build time or bandwidth used to achieve the upgrade.
The @code{non-core} subset refers to the remaining packages. It is
typically useful in cases where an update of the core packages would be
inconvenient.
@end table
In addition, @command{guix refresh} can be passed one or more package
names, as in this example:
@example
guix refresh -u emacs idutils
@end example
@noindent
The command above specifically updates the @code{emacs} and
@code{idutils} packages. The @code{--select} option would have no
effect in this case.
When considering whether to upgrade a package, it is sometimes
convenient to know which packages would be affected by the upgrade and
should be checked for compatibility. For this the following option may
be used when passing @command{guix refresh} one or more package names:
@table @code
@item --list-dependent
@itemx -l
List top-level dependent packages that would need to be rebuilt as a
result of upgrading one or more packages.
@end table
Be aware that the @code{--list-dependent} option only
@emph{approximates} the rebuilds that would be required as a result of
an upgrade. More rebuilds might be required under some circumstances.
@example
$ guix refresh --list-dependent flex
Building the following 120 packages would ensure 213 dependent packages are rebuilt:
hop-2.4.0 geiser-0.4 notmuch-0.18 mu-0.9.9.5 cflow-1.4 idutils-4.6 @dots{}
@end example
The command above lists a set of packages that could be built to check
for compatibility with an upgraded @code{flex} package.
The following options can be used to customize GnuPG operation:
@table @code
@item --gpg=@var{command}
Use @var{command} as the GnuPG 2.x command. @var{command} is searched
for in @code{$PATH}.
@item --key-download=@var{policy}
Handle missing OpenPGP keys according to @var{policy}, which may be one
of:
@table @code
@item always
Always download missing OpenPGP keys from the key server, and add them
to the user's GnuPG keyring.
@item never
Never try to download missing OpenPGP keys. Instead just bail out.
@item interactive
When a package signed with an unknown OpenPGP key is encountered, ask
the user whether to download it or not. This is the default behavior.
@end table
@item --key-server=@var{host}
Use @var{host} as the OpenPGP key server when importing a public key.
@end table
@node Invoking guix lint
@section Invoking @command{guix lint}
The @command{guix lint} is meant to help package developers avoid common
errors and use a consistent style. It runs a number of checks on a
given set of packages in order to find common mistakes in their
definitions. Available @dfn{checkers} include (see
@code{--list-checkers} for a complete list):
@table @code
@item synopsis
@itemx description
Validate certain typographical and stylistic rules about package
descriptions and synopses.
@item inputs-should-be-native
Identify inputs that should most likely be native inputs.
@item source
@itemx home-page
Probe @code{home-page} and @code{source} URLs and report those that are
invalid.
@end table
The general syntax is:
@example
guix lint @var{options} @var{package}@dots{}
@end example
If no package is given on the command line, then all packages are checked.
The @var{options} may be zero or more of the following:
@table @code
@item --checkers
@itemx -c
Only enable the checkers specified in a comma-separated list using the
names returned by @code{--list-checkers}.
@item --list-checkers
@itemx -l
List and describe all the available checkers that will be run on packages
and exit.
@end table
@node Invoking guix environment
@section Invoking @command{guix environment}
@cindex reproducible build environments
The purpose of @command{guix environment} is to assist hackers in
creating reproducible development environments without polluting their
package profile. The @command{guix environment} tool takes one or more
packages, builds all of the necessary inputs, and creates a shell
environment to use them.
The general syntax is:
@example
guix environment @var{options} @var{package}@dots{}
@end example
The following examples spawns a new shell that is capable of building
the GNU Guile source code:
@example
guix environment guile
@end example
If the specified packages are not built yet, @command{guix environment}
automatically builds them. The new shell's environment is an augmented
version of the environment that @command{guix environment} was run in.
It contains the necessary search paths for building the given package
added to the existing environment variables. To create a ``pure''
environment in which the original environment variables have been unset,
use the @code{--pure} option.
Additionally, more than one package may be specified, in which case the
union of the inputs for the given packages are used. For example, the
command below spawns a shell where all of the dependencies of both Guile
and Emacs are available:
@example
guix environment guile emacs
@end example
Sometimes an interactive shell session is not desired. The
@code{--exec} option can be used to specify the command to run instead.
@example
guix environment guile --exec=make
@end example
The following options are available:
@table @code
@item --expression=@var{expr}
@itemx -e @var{expr}
Create an environment for the package that @var{expr} evaluates to.
@item --load=@var{file}
@itemx -l @var{file}
Create an environment for the package that the code within @var{file}
evaluates to.
@item --exec=@var{command}
@item -E @var{command}
Execute @var{command} in the new environment.
@item --pure
Unset existing environment variables when building the new environment.
This has the effect of creating an environment in which search paths
only contain package inputs.
@item --search-paths
Display the environment variable definitions that make up the
environment.
@end table
It also supports all of the common build options that @command{guix
build} supports (@pxref{Invoking guix build, common build options}).
@c *********************************************************************
@node GNU Distribution
@chapter GNU Distribution
@cindex Guix System Distribution
@cindex GSD
Guix comes with a distribution of the GNU system consisting entirely of
free software@footnote{The term ``free'' here refers to the
@url{http://www.gnu.org/philosophy/free-sw.html,freedom provided to
users of that software}.}. The
distribution can be installed on its own (@pxref{System Installation}),
but it is also possible to install Guix as a package manager on top of
an installed GNU/Linux system (@pxref{Installation}). To distinguish
between the two, we refer to the standalone distribution as the Guix
System Distribution, or GNU@tie{}GSD.
The distribution provides core GNU packages such as GNU libc, GCC, and
Binutils, as well as many GNU and non-GNU applications. The complete
list of available packages can be browsed
@url{http://www.gnu.org/software/guix/package-list.html,on-line} or by
running @command{guix package} (@pxref{Invoking guix package}):
@example
guix package --list-available
@end example
Our goal has been to provide a practical 100% free software distribution of
Linux-based and other variants of GNU, with a focus on the promotion and
tight integration of GNU components, and an emphasis on programs and
tools that help users exert that freedom.
Packages are currently available on the following platforms:
@table @code
@item x86_64-linux
Intel/AMD @code{x86_64} architecture, Linux-Libre kernel;
@item i686-linux
Intel 32-bit architecture (IA32), Linux-Libre kernel;
@item armhf-linux
ARMv7-A architecture with hard float, Thumb-2 and VFP3D16 coprocessor,
using the EABI hard-float ABI, and Linux-Libre kernel.
@item mips64el-linux
little-endian 64-bit MIPS processors, specifically the Loongson series,
n32 application binary interface (ABI), and Linux-Libre kernel.
@end table
GSD itself is currently only available on @code{i686} and @code{x86_64}.
@noindent
For information on porting to other architectures or kernels,
@xref{Porting}.
@menu
* System Installation:: Installing the whole operating system.
* System Configuration:: Configuring the operating system.
* Installing Debugging Files:: Feeding the debugger.
* Security Updates:: Deploying security fixes quickly.
* Package Modules:: Packages from the programmer's viewpoint.
* Packaging Guidelines:: Growing the distribution.
* Bootstrapping:: GNU/Linux built from scratch.
* Porting:: Targeting another platform or kernel.
@end menu
Building this distribution is a cooperative effort, and you are invited
to join! @xref{Contributing}, for information about how you can help.
@node System Installation
@section System Installation
@cindex Guix System Distribution
This section explains how to install the Guix System Distribution
on a machine. The Guix package manager can
also be installed on top of a running GNU/Linux system,
@pxref{Installation}.
@ifinfo
@c This paragraph is for people reading this from tty2 of the
@c installation image.
You're reading this documentation with an Info reader. For details on
how to use it, hit the @key{RET} key (``return'' or ``enter'') on the
link that follows: @pxref{Help,,, info, Info: An Introduction}. Hit
@kbd{l} afterwards to come back here.
@end ifinfo
@subsection Limitations
As of version @value{VERSION}, the Guix System Distribution (GSD) is
not production-ready. It may contain bugs and lack important
features. Thus, if you are looking for a stable production system that
respects your freedom as a computer user, a good solution at this point
is to consider @url{http://www.gnu.org/distros/free-distros.html, one of
more established GNU/Linux distributions}. We hope you can soon switch
to the GSD without fear, of course. In the meantime, you can
also keep using your distribution and try out the package manager on top
of it (@pxref{Installation}).
Before you proceed with the installation, be aware of the following
noteworthy limitations applicable to version @value{VERSION}:
@itemize
@item
The installation process does not include a graphical user interface and
requires familiarity with GNU/Linux (see the following subsections to
get a feel of what that means.)
@item
The system does not yet provide GNOME and KDE; it provides Xfce, though,
if graphical desktop environments are your thing.
@item
Support for the Logical Volume Manager (LVM) is missing.
@item
Few system services are currently supported out-of-the-box
(@pxref{Services}).
@item
On the order of 1,200 packages are available, which means that you may
occasionally find that a useful package is missing.
@end itemize
You've been warned. But more than a disclaimer, this is an invitation
to report issues (and success stories!), and join us in improving it.
@xref{Contributing}, for more info.
@subsection USB Stick Installation
An installation image for USB sticks can be downloaded from
@url{ftp://alpha.gnu.org/gnu/guix/gsd-usb-install-@value{VERSION}.@var{system}.xz},
where @var{system} is one of:
@table @code
@item x86_64-linux
for a GNU/Linux system on Intel/AMD-compatible 64-bit CPUs;
@item i686-linux
for a 32-bit GNU/Linux system on Intel-compatible CPUs.
@end table
This image contains a single partition with the tools necessary for an
installation. It is meant to be copied @emph{as is} to a large-enough
USB stick.
To copy the image to a USB stick, follow these steps:
@enumerate
@item
Decompress the image using the @command{xz} command:
@example
xz -d gsd-usb-install-@value{VERSION}.@var{system}.xz
@end example
@item
Insert a USB stick of 1@tie{}GiB or more in your machine, and determine
its device name. Assuming that USB stick is known as @file{/dev/sdX},
copy the image with:
@example
dd if=gsd-usb-install-@value{VERSION}.x86_64 of=/dev/sdX
@end example
Access to @file{/dev/sdX} usually requires root privileges.
@end enumerate
Once this is done, you should be able to reboot the system and boot from
the USB stick. The latter usually requires you to get in the BIOS' boot
menu, where you can choose to boot from the USB stick.
@subsection Preparing for Installation
Once you have successfully booted the image on the USB stick, you should
end up with a root prompt. Several console TTYs are configured and can
be used to run commands as root. TTY2 shows this documentation,
browsable using the Info reader commands (@pxref{Help,,, info, Info: An
Introduction}).
To install the system, you would:
@enumerate
@item
Configure the network, by running @command{dhclient eno1} (to get an
automatically assigned IP address from the wired network interface
controller@footnote{
@c http://cgit.freedesktop.org/systemd/systemd/tree/src/udev/udev-builtin-net_id.c#n20
The name @code{eno1} is for the first on-board Ethernet controller. The
interface name for an Ethernet controller that is in the first slot of
the first PCI bus, for instance, would be @code{enp1s0}. Use
@command{ifconfig -a} to list all the available network interfaces.}),
or using the @command{ifconfig} command.
The system automatically loads drivers for your network interface
controllers.
Setting up network access is almost always a requirement because the
image does not contain all the software and tools that may be needed.
@item
Unless this has already been done, you must partition and format the
target partitions.
Preferably, assign partitions a label so that you can easily and
reliably refer to them in @code{file-system} declarations (@pxref{File
Systems}). This is typically done using the @code{-L} option of
@command{mkfs.ext4} and related commands.
The installation image includes Parted (@pxref{Overview,,, parted, GNU
Parted User Manual}), @command{fdisk}, Cryptsetup/LUKS for disk
encryption, and e2fsprogs, the suite of tools to manipulate
ext2/ext3/ext4 file systems.
@item
Once that is done, mount the target root partition under @file{/mnt}.
@item
Lastly, run @code{deco start cow-store /mnt}.
This will make @file{/gnu/store} copy-on-write, such that packages added
to it during the installation phase will be written to the target disk
rather than kept in memory.
@end enumerate
@subsection Proceeding with the Installation
With the target partitions ready, you now have to edit a file and
provide the declaration of the operating system to be installed. To
that end, the installation system comes with two text editors: GNU nano
(@pxref{Top,,, nano, GNU nano Manual}), and GNU Zile, an Emacs clone.
It is better to store that file on the target root file system, say, as
@file{/mnt/etc/config.scm}.
A minimal operating system configuration, with just the bare minimum and
only a root account would look like this (on the installation system,
this example is available as @file{/etc/configuration-template.scm}):
@example
@include os-config.texi
@end example
@noindent
For more information on @code{operating-system} declarations,
@pxref{Using the Configuration System}.
Once that is done, the new system must be initialized (remember that the
target root file system is mounted under @file{/mnt}):
@example
guix system init /mnt/etc/config.scm /mnt
@end example
@noindent
This will copy all the necessary files, and install GRUB on
@file{/dev/sdX}, unless you pass the @option{--no-grub} option. For
more information, @pxref{Invoking guix system}. This command may trigger
downloads or builds of missing packages, which can take some time.