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Distribute software with GNU Guix

-*- mode: org; coding: utf-8; -*-

Introduction

Here we discuss ‘easy’ tar-ball deployment of GNU Guix packages similar to the binary distribution of GNU Guix itself (see download).

How does Guix do it?

WARNING: this is an advanced topic, you may want to skip to the next section.

The source tree contains ./gnu/system/install.scm. This module provides an ‘operating-system’ definition for use on images for USB sticks etc., for the installation of the GNU system. It has the function ‘self-contained-tarball’.

This in turn gets invoked from ./build-aux/make-binary-tarball.scm which is invoked from the command line with (see the main ./Makefile).

# The self-contained tarball.
guix-binary.%.tar.xz:
  $(AM_V_GEN)GUIX_PACKAGE_PATH= \
  $(top_builddir)/pre-inst-env "$(GUILE)"     \
    "$(top_srcdir)/build-aux/make-binary-tarball.scm" "$*" "$@"

The function ‘self-contained-tarball’ returns a compressed tar ball containing a store initialized with the closure of GUIX. The tarball contains gnu/store, /var/guix, and a profile under /root.guix-profile where GUIX is installed. It is a short function, so we can list it here with a few extra comments

(define* (self-contained-tarball #:key (guix guix))
  ;; fetch the derivation for the guix package:
  (mlet %store-monad ((profile (profile-derivation
                                (manifest
                                 (list (package->manifest-entry guix))))))
    (define build
      ;; import build-time modules from the Guix source
      (with-imported-modules '((guix build utils)
                               (guix build store-copy)
                               (gnu build install))
        #~(begin
            (use-modules (guix build utils)
                         (gnu build install))

            (define %root "root")

            ;; set the search path for binaries to find tar and xz
            (setenv "PATH"
                    (string-append #$guix "/sbin:" #$tar "/bin:" #$xz "/bin"))
            ;; create the root ~/.guix-profile/ for guix
            (populate-single-profile-directory %root
                                               #:profile #$profile
                                               #:closure "profile"
                                               #:deduplicate? #f)

            ;; Create the tarball.  Use GNU format so there's no file name
            ;; length limitation.
            (with-directory-excursion %root
              (zero? (system* "tar" "--xz" "--format=gnu"
                              ;; Avoid non-determinism in the archive.  Use
                              ;; mtime = 1, not zero, because that is what the
                              ;; daemon does for files in the store (see the
                              ;; 'mtimeStore' constant in local-store.cc.)
                              "--sort=name"
                              "--mtime=@1"        ;for files in /var/guix
                              "--owner=root:0"
                              "--group=root:0"

                              "--check-links"
                              "-cvf" #$output
                              ;; Avoid adding / and /var to the tarball, so
                              ;; that the ownership and permissions of those
                              ;; directories will not be overwritten when
                              ;; extracting the archive.  Do not include /root
                              ;; because the root account might have a
                              ;; different home directory.
                              "./var/guix"
                              (string-append "." (%store-directory))))))))

    ;; and build it using above build function
    (gexp->derivation "guix-tarball.tar.xz" build
                      #:references-graphs `(("profile" ,profile)))))

In short the derivation gets build from its derivation and the result gets packed into a tar ball. Let’s try it:

make guix-binary.x86_64-linux.tar.xz

Runs the tests and creates the tarball. Pretty cool!

Rolling our own

Our users will want to deploy our tar ball on a fresh system. If they already have GNU Guix they can use the normal Guix installation path. The feature of a binary installation (here) is specifically for new users.

Guix also has the archive option which can create an archive of a software package with its dependencies. To unpack the archive you need GNU guix installed and update the access key. We can also provide that, but here we discuss creating a one-time binary installation.

We could include Guix itself in the tar ball - which would allow us to build a store that is guix ‘ready’.

Anyway, there are a few options. The one thing I would like to try is to create an archive, install that in a container and tarball that up for distribution.

Creating the tarball

To package up the ‘hello’ package:

./pre-inst-env guix environment --container --ad-hoc hello tar gzip -- tar cvzf test.tgz /gnu/store

results in a minimalistic hello package with all dependencies - sized 28Mb.

That was one single command.

Next, unpack the software on a fresh Linux (e.g. using a VM or container):

cd /
tar xvzf test.tgz

Now the files are in /gnu and you should be able to run either directly

/gnu/store/zy5aanymkq37l91yhq0xa6rddv1skl6s-hello-2.10/bin/hello
  Hello, world!

or by using the profile

/gnu/store/hfmsjsvx1p68wbx0fli4icg20jsb5j4v-profile/bin/hello
  Hello, world!

This implies we can combine any number of software packages with dependencies and tar it all up for distribution. It will also unpack in a Docker container without special privileges.

Create relocatable installer

Starting from above tar ball we can make a relocatable binary installer using a few tricks. Unpack the tar ball somewhere

mkdir hello
cd hello
tar xvzf ../test.tgz

Now the files should be in ./gnu/store

ls ./gnu/store

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