|
- -*- mode: org; coding: utf-8; -*-
-
- #+TITLE: Hacking GNU Guix and Its Incredible Distro
-
- Copyright © 2012, 2013 Ludovic Courtès <ludo@gnu.org>
-
- Copying and distribution of this file, with or without modification,
- are permitted in any medium without royalty provided the copyright
- notice and this notice are preserved.
-
-
- * Running Guix before it is installed
-
- Command-line tools can be used even if you have not run "make install".
- To do that, prefix each command with ‘./pre-inst-env’, as in:
-
- ./pre-inst-env guix-build --help
-
- Similarly, for a Guile session using the Guix modules:
-
- ./pre-inst-env guile -c '(use-modules (guix utils)) (pk (%current-system))'
-
- The ‘pre-inst-env’ script sets up all the environment variables
- necessary to support this.
-
- * Adding new packages
-
- Package recipes in Guix look like this:
-
- #+BEGIN_SRC scheme
- (package
- (name "nettle")
- (version "2.5")
- (source
- (origin
- (method url-fetch)
- (uri (string-append "mirror://gnu/nettle/nettle-"
- version ".tar.gz"))
- (sha256
- (base32
- "0wicr7amx01l03rm0pzgr1qvw3f9blaw17vjsy1301dh13ll58aa"))))
- (build-system gnu-build-system)
- (inputs `(("m4" ,m4)))
- (propagated-inputs `(("gmp" ,gmp)))
- (home-page
- "http://www.lysator.liu.se/~nisse/nettle/")
- (synopsis "GNU Nettle, a cryptographic library")
- (description
- "Nettle is a cryptographic library...")
- (license gpl2+))
- #+END_SRC
-
- Such a recipe can be written by hand, and then tested by running
- ‘./pre-inst-env guix-build nettle’.
-
- When writing the recipe, the base32-encoded SHA256 hash of the source
- code tarball, which can be seen in the example above, can be obtained by
- running:
-
- guix-download http://ftp.gnu.org/gnu/nettle/nettle-2.5.tar.gz
-
- Alternatively, it is possible to semi-automatically import recipes from
- the [[http://nixos.org/nixpkgs/][Nixpkgs]] software distribution using this command:
-
- guix-import /path/to/nixpkgs/checkout nettle
-
- The command automatically fetches and converts to Guix the “Nix
- expression” of Nettle.
-
- * Porting the Guix distro on a new platform
-
- ** Introduction
-
- Unlike Make or similar build tools, Guix requires absolutely /all/ the
- dependencies of a build process to be specified.
-
- For a user-land software distribution, that means that the process that
- builds GCC (then used to build all other programs) must itself be
- specified; and the process to build the C library to build that GCC; and
- the process to build the GCC to build that library; and... See the
- problem? Chicken-and-egg.
-
- To break that cycle, the distro starts from a set of pre-built
- binaries–usually referred to as “bootstrap binaries.” These include
- statically-linked versions of Guile, GCC, Coreutils, Make, Grep, sed,
- etc., and the GNU C Library.
-
- This section describes how to build those bootstrap binaries when
- porting to a new platform.
-
- ** When the platform is supported by Nixpkgs
-
- In that case, the easiest thing is to bootstrap the distro using
- binaries from Nixpkgs.
-
- To do that, you need to comment out the definitions of
- ‘%bootstrap-guile’ and ‘%bootstrap-inputs’ in distro/packages/bootstrap.scm
- to force the use of Nixpkgs derivations. For instance, when porting to
- ‘i686-linux’, you should redefine these variables along these lines:
-
- #+BEGIN_SRC scheme
- (define %bootstrap-guile
- (nixpkgs-derivation "guile" "i686-linux"))
-
- (define %bootstrap-inputs
- (compile-time-value
- `(("libc" ,(nixpkgs-derivation "glibc" "i686-linux"))
- ,@(map (lambda (name)
- (list name (nixpkgs-derivation name "i686-linux")))
- '("gnutar" "gzip" "bzip2" "xz" "patch"
- "coreutils" "gnused" "gnugrep" "bash"
- "gawk" ; used by `config.status'
- "gcc" "binutils")))))
- #+END_SRC
-
- That should allow the distro to be bootstrapped.
-
- Then, the tarballs containing the initial binaries of Guile, Coreutils,
- GCC, libc, etc. need to be built. To that end, run the following
- commands:
-
- #+BEGIN_SRC sh
- ./pre-inst-env guix-build \
- -e '(@ (distro packages make-bootstrap) bootstrap-tarballs)' \
- --system=i686-linux
-
- #+END_SRC
-
- These should build tarballs containing statically-linked tools usable on
- that system.
-
- In the source tree, you need to install binaries for ‘mkdir’, ‘bash’,
- ‘tar’, and ‘xz’ under ‘distro/packages/bootstrap/i686-linux’. These
- binaries can be extracted from the static-binaries tarball built above.
-
- A rule for ‘distro/packages/bootstrap/i686-linux/guile-2.0.7.tar.xz’
- needs to be added in ‘Makefile.am’, with the appropriate hexadecimal
- vrepresentation of its SHA256 hash.
-
- You may then revert your changes to ‘bootstrap.scm’. For the variables
- ‘%bootstrap-coreutils&co’, ‘%bootstrap-binutils’, ‘%bootstrap-glibc’,
- and ‘%bootstrap-gcc’, the expected SHA256 of the corresponding tarballs
- for ‘i686-linux’ (built above) must be added.
-
- This should be enough to bootstrap the distro without resorting to
- Nixpkgs.
-
- ** When the platform is *not* supported by Nixpkgs
-
- In that case, the bootstrap binaries should be built using whatever
- tools are available on the target platform. That is, the tarballs and
- binaries show above must first be built manually, using the available
- tools.
-
- They should have the same properties as those built by the Guix recipes
- shown above. For example, all the binaries (except for glibc) must be
- statically-linked; the bootstrap Guile must be relocatable (see patch in
- the Guix distro); the static-binaries tarball must contain the same
- programs (Coreutils, Grep, sed, Awk, etc.); and so on.
|