178 lines
6.5 KiB
Org Mode
178 lines
6.5 KiB
Org Mode
-*- 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.
|
||
|
||
* The Perfect Setup
|
||
|
||
The Perfect Setup to hack on Guix is basically the perfect setup used
|
||
for Guile hacking (info "(guile) Using Guile in Emacs"). First, you
|
||
need more than an editor, you need [[http://www.gnu.org/software/emacs][Emacs]], empowered by the wonderful
|
||
[[http://nongnu.org/geiser/][Geiser]].
|
||
|
||
Geiser allows for interactive and incremental development from within
|
||
Emacs: code compilation and evaluation from within buffers, access to
|
||
on-line documentation (docstrings), context-sensitive completion, M-. to
|
||
jump to an object definition, a REPL to try out your code, and more.
|
||
|
||
To actually edit the code, Emacs already has a neat Scheme mode. But in
|
||
addition to that, you must not miss [[http://www.emacswiki.org/emacs/ParEdit][Paredit]]. It provides facilities to
|
||
directly operate on the syntax tree, such as raising an s-expression or
|
||
wrapping it, swallowing or rejecting the following s-expression, etc.
|
||
|
||
* 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 -K \
|
||
-e '(@ (gnu 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.
|
||
|