GNU Guix Reference Manual

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GNU Guix

This document describes GNU Guix version 0.7, a functional package management tool written for the GNU system.


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1 Introduction

GNU Guix1 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.

The term 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 containers), where only their explicit inputs are visible.

The result of package build functions is cached in the file system, in a special directory called the store (see The Store). Each package is installed in a directory of its own, in the store—by default under /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 (see Features).

Guix has a command-line interface, which allows users to build, install, upgrade, and remove packages, as well as a Scheme programming interface.

Last but not least, Guix is used to build a distribution of the GNU system, with many GNU and non-GNU free software packages. See GNU Distribution.


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2 Installation

GNU Guix is available for download from its website at 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, see System Installation.

The build procedure for Guix is the same as for other GNU software, and is not covered here. Please see the files README and INSTALL in the Guix source tree for additional details.


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2.1 Requirements

GNU Guix depends on the following packages:

Unless --disable-daemon was passed to configure, the following packages are also needed:

When a working installation of the Nix package manager is available, you can instead configure Guix with --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 configure not only the same --with-store-dir value, but also the same --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 --with-store-dir=/nix/store and --localstatedir=/nix/var. Note that --disable-daemon is not required if your goal is to share the store with Nix.


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2.2 Setting Up the Daemon

Operations such as building a package or running the garbage collector are all performed by a specialized process, the 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 guix package and guix build communicate with the daemon (via remote procedure calls) to instruct it what to do.

The following sections explain how to prepare the build daemon’s environment.


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2.2.1 Build Environment Setup

In a standard multi-user setup, Guix and its daemon—the guix-daemon program—are installed by the system administrator; /gnu/store is owned by root and guix-daemon runs as 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.

When guix-daemon runs as root, you may not want package build processes themselves to run as root too, for obvious security reasons. To avoid that, a special pool of 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 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 (see Introduction).

On a GNU/Linux system, a build user pool may be created like this (using Bash syntax and the shadow commands):

# 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

The guix-daemon program may then be run as root with:

# guix-daemon --build-users-group=guix-builder

This way, the daemon starts build processes in a chroot, under one of the guix-builder users. On GNU/Linux, by default, the chroot environment contains nothing but:

If you are installing Guix as an unprivileged user, it is still possible to run 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 pure functions.


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2.2.2 Using the Offload Facility

When desired, the build daemon can offload derivation builds to other machines running Guix, using the offload build hook. When that feature is enabled, a list of user-specified build machines is read from /etc/guix/machines.scm; anytime a build is requested, for instance via 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., 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 /etc/guix/machines.scm file typically looks like this:

(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"))))

In the example above we specify a list of two build machines, one for the x86_64 architecture and one for the mips64el architecture.

In fact, this file is—not surprisingly!—a Scheme file that is evaluated when the offload hook is started. Its return value must be a list of 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 (see Guile-Avahi in Using Avahi in Guile Scheme Programs).

The compulsory fields for a build-machine declaration are:

name

The remote machine’s host name.

system

The remote machine’s system type.

user

The user account to use when connecting to the remote machine over SSH. Note that the SSH key pair must not be passphrase-protected, to allow non-interactive logins.

A number of optional fields may be specified:

port

Port number of the machine’s SSH server (default: 22).

private-key

The SSH private key file to use when connecting to the machine.

parallel-builds

The number of builds that may run in parallel on the machine (1 by default.)

speed

A “relative speed factor”. The offload scheduler will tend to prefer machines with a higher speed factor.

features

A list of strings denoting specific features supported by the machine. An example is "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.

The guix command must be in the search path on the build machines, since offloading works by invoking the guix archive and guix build commands.

There’s one last thing to do once 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 (see Invoking guix archive):

# guix archive --generate-key

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.


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2.3 Invoking guix-daemon

The 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 root like this:

# guix-daemon --build-users-group=guix-builder

For details on how to set it up, Setting Up the Daemon.

By default, guix-daemon launches build processes under different UIDs, taken from the build group specified with --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 (see derivation), plus a set of specific system directories. By default, the latter contains /dev and /dev/pts. Furthermore, on GNU/Linux, the build environment is a 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 (see Features).

The following command-line options are supported:

--build-users-group=group

Take users from group to run build processes (see build users).

--no-substitutes

Do not use substitutes for build products. That is, always build things locally instead of allowing downloads of pre-built binaries (see Substitutes).

By default substitutes are used, unless the client—such as the guix package command—is explicitly invoked with --no-substitutes.

When the daemon runs with --no-substitutes, clients can still explicitly enable substitution via the set-build-options remote procedure call (see The Store).

--no-build-hook

Do not use the 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 (see Daemon Offload Setup).

--cache-failures

Cache build failures. By default, only successful builds are cached.

--cores=n
-c n

Use n CPU cores to build each derivation; 0 means as many as available.

The default value is 1, but it may be overridden by clients, such as the --cores option of guix build (see Invoking guix build).

The effect is to define the NIX_BUILD_CORES environment variable in the build process, which can then use it to exploit internal parallelism—for instance, by running make -j$NIX_BUILD_CORES.

--max-jobs=n
-M n

Allow at most n build jobs in parallel. The default value is 1.

--debug

Produce debugging output.

This is useful to debug daemon start-up issues, but then it may be overridden by clients, for example the --verbosity option of guix build (see Invoking guix build).

--chroot-directory=dir

Add dir to the build chroot.

Doing this may change the result of build processes—for instance if they use optional dependencies found in 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.

--disable-chroot

Disable chroot builds.

Using this option is not recommended since, again, it would allow build processes to gain access to undeclared dependencies.

--disable-log-compression

Disable compression of the build logs.

Unless --lose-logs is used, all the build logs are kept in the localstatedir. To save space, the daemon automatically compresses them with bzip2 by default. This option disables that.

--disable-store-optimization

Disable automatic file “deduplication” in the store.

By default, files added to the store are automatically “deduplicated”: if a newly added file is identical as another one found in the store, the daemon makes the new file a hard link to the other file. This slightly increases the input/output load at the end of a build process. This option disables this.

--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 .drv files. The default is “no”, meaning that derivation outputs are kept only if they are GC roots.

--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., .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 --gc-keep-derivations and --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.

--impersonate-linux-2.6

On Linux-based systems, impersonate Linux 2.6. This means that the kernel’s 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.

--lose-logs

Do not keep build logs. By default they are kept under localstatedir/nix/log.

--system=system

Assume system as the current system type. By default it is the architecture/kernel pair found at configure time, such as x86_64-linux.

--listen=socket

Listen for connections on socket, the file name of a Unix-domain socket. The default socket is 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.


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3 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.


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3.1 Features

When using Guix, each package ends up in the package store, in its own directory—something that resembles /gnu/store/xxx-package-1.2, where xxx is a base32 string.

Instead of referring to these directories, users have their own profile, which points to the packages that they actually want to use. These profiles are stored within each user’s home directory, at $HOME/.guix-profile.

For example, alice installs GCC 4.7.2. As a result, /home/alice/.guix-profile/bin/gcc points to /gnu/store/…-gcc-4.7.2/bin/gcc. Now, on the same machine, bob had already installed GCC 4.8.0. The profile of bob simply continues to point to /gnu/store/…-gcc-4.8.0/bin/gcc—i.e., both versions of GCC coexist on the same system without any interference.

The guix package command is the central tool to manage packages (see Invoking guix package). It operates on those per-user profiles, and can be used with normal user privileges.

The command provides the obvious install, remove, and upgrade operations. Each invocation is actually a transaction: either the specified operation succeeds, or nothing happens. Thus, if the 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 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 (see Using the Configuration System).

All those packages in the package store may be garbage-collected. Guix can determine which packages are still referenced by the user profiles, and remove those that are provably no longer referenced (see Invoking guix gc). Users may also explicitly remove old generations of their profile so that the packages they refer to can be collected.

Finally, Guix takes a purely functional approach to package management, as described in the introduction (see Introduction). Each /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 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 (see container).

This foundation allows Guix to support transparent binary/source deployment. When a pre-built binary for a /gnu/store item is available from an external source—a substitute, Guix just downloads it and unpacks it; otherwise, it builds the package from source, locally (see Substitutes).


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3.2 Invoking guix package

The 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 (see Features). Its syntax is:

guix package options

Primarily, 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 lua and install guile and guile-cairo in a single transaction:

guix package -r lua -i guile guile-cairo

For each user, a symlink to the user’s default profile is automatically created in $HOME/.guix-profile. This symlink always points to the current generation of the user’s default profile. Thus, users can add $HOME/.guix-profile/bin to their PATH environment variable, and so on.

In a multi-user setup, user profiles must be stored in a place registered as a garbage-collector root, which $HOME/.guix-profile points to (see Invoking guix gc). That directory is normally localstatedir/profiles/per-user/user, where localstatedir is the value passed to configure as --localstatedir, and user is the user name. It must be created by root, with user as the owner. When it does not exist, or is not owned by user, guix package emits an error about it.

The options can be among the following:

--install=package
-i package

Install the specified packages.

Each package may specify either a simple package name, such as guile, or a package name followed by a hyphen and version number, such as guile-1.8.8. If no version number is specified, the newest available version will be selected. In addition, package may contain a colon, followed by the name of one of the outputs of the package, as in gcc:doc or binutils-2.22:lib (see Packages with Multiple Outputs). Packages with a corresponding name (and optionally version) are searched for among the GNU distribution modules (see Package Modules).

Sometimes packages have 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 --search-paths below). Any missing or possibly incorrect environment variable definitions are reported here.

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.

--install-from-expression=exp
-e exp

Install the package exp evaluates to.

exp must be a Scheme expression that evaluates to a <package> object. This option is notably useful to disambiguate between same-named variants of a package, with expressions such as (@ (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.

--remove=package
-r package

Remove the specified packages.

As for --install, each package may specify a version number and/or output name in addition to the package name. For instance, -r glibc:debug would remove the debug output of glibc.

--upgrade[=regexp …]
-u [regexp …]

Upgrade all the installed packages. If one or more regexps are specified, upgrade only installed packages whose name matches a 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 guix pull (see Invoking guix pull).

--roll-back

Roll back to the previous generation of the profile—i.e., undo the last transaction.

When combined with options such as --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 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.

--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 search paths for files used by some of the installed packages.

For example, GCC needs the CPATH and LIBRARY_PATH environment variables to be defined so it can look for headers and libraries in the user’s profile (see Environment Variables in Using the GNU Compiler Collection (GCC)). If GCC and, say, the C library are installed in the profile, then --search-paths will suggest setting these variables to profile/include and profile/lib, respectively.

--profile=profile
-p profile

Use profile instead of the user’s default profile.

--verbose

Produce verbose output. In particular, emit the environment’s build log on the standard error port.

--bootstrap

Use the bootstrap Guile to build the profile. This option is only useful to distribution developers.

In addition to these actions guix package supports the following options to query the current state of a profile, or the availability of packages:

--search=regexp
-s regexp

List the available packages whose synopsis or description matches regexp. Print all the meta-data of matching packages in recutils format (see GNU recutils databases in GNU recutils manual).

This allows specific fields to be extracted using the recsel command, for instance:

$ guix package -s malloc | recsel -p name,version
name: glibc
version: 2.17

name: libgc
version: 7.2alpha6

Similarly, to show the name of all the packages available under the terms of the GNU LGPL version 3:

$ guix package -s "" | recsel -p name -e 'license ~ "LGPL 3"'
name: elfutils

name: gmp
…
--show=package

Show details about package, taken from the list of available packages, in recutils format (see GNU recutils databases in GNU recutils manual).

$ guix package --show=python | recsel -p name,version
name: python
version: 2.7.6

name: python
version: 3.3.5

You may also specify the full name of a package to only get details about a specific version of it:

$ guix package --show=python-3.3.5 | recsel -p name,version
name: python
version: 3.3.5
--list-installed[=regexp]
-I [regexp]

List the currently installed packages in the specified profile, with the most recently installed packages shown last. When regexp is specified, list only installed packages whose name matches 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, out for the default output, include for its headers, etc.), and the path of this package in the store.

--list-available[=regexp]
-A [regexp]

List packages currently available in the software distribution (see GNU Distribution). When regexp is specified, list only installed packages whose name matches regexp.

For each package, print the following items separated by tabs: its name, its version string, the parts of the package (see Packages with Multiple Outputs), and the source location of its definition.

--list-generations[=pattern]
-l [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 (see Packages with Multiple Outputs), and the location of this package in the store.

When pattern is used, the command returns only matching generations. Valid patterns include:

--delete-generations[=pattern]
-d [pattern]

When pattern is omitted, delete all generations except the current one.

This command accepts the same patterns as --list-generations. When pattern is specified, delete the matching generations. When pattern specifies a duration, generations older than the specified duration match. For instance, --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.

Finally, since guix package may actually start build processes, it supports all the common build options that guix build supports (see common build options).


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3.3 Substitutes

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 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 (see 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 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.

To allow Guix to download substitutes from hydra.gnu.org, you must add its public key to the access control list (ACL) of archive imports, using the guix archive command (see Invoking guix archive). Doing so implies that you trust hydra.gnu.org to not be compromised and to serve genuine substitutes.

This public key is installed along with Guix, in prefix/share/guix/hydra.gnu.org.pub, where prefix is the installation prefix of Guix. If you installed Guix from source, make sure you checked the GPG signature of guix-0.7.tar.gz, which contains this public key file. Then, you can run something like this:

# guix archive --authorize < hydra.gnu.org.pub

Once this is in place, the output of a command like guix build should change from something like:

$ 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
…

to something like:

$ 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
…

This indicates that substitutes from 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 guix-daemon with --no-substitutes (see Invoking guix-daemon). It can also be disabled temporarily by passing the --no-substitutes option to guix package, 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 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 hydra.gnu.org is less of an interesting target.

Guix has the foundations to maximize build reproducibility (see 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 guix-devel@gnu.org.


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3.4 Packages with Multiple Outputs

Often, packages defined in Guix have a single output—i.e., the source package leads exactly one directory in the store. When running guix package -i glibc, one installs the default output of the GNU libc package; the default output is called out, but its name can be omitted as shown in this command. In this particular case, the default output of 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 doc. To install the main GLib output, which contains everything but the documentation, one would run:

guix package -i glib

The command to install its documentation is:

guix package -i glib:doc

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 lib for libraries and possibly header files, bin for stand-alone programs, and debug for debugging information (see Installing Debugging Files). The outputs of a packages are listed in the third column of the output of guix package --list-available (see Invoking guix package).


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3.5 Invoking guix gc

Packages that are installed but not used may be garbage-collected. The guix gc command allows users to explicitly run the garbage collector to reclaim space from the /gnu/store directory.

The garbage collector has a set of known roots: any file under /gnu/store reachable from a root is considered live and cannot be deleted; any other file is considered dead and may be deleted. The set of garbage collector roots includes default user profiles, and may be augmented with guix build --root, for example (see Invoking guix build).

Prior to running 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 guix package --delete-generations (see Invoking guix package).

The 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 --delete option), or to print garbage-collector information. The available options are listed below:

--collect-garbage[=min]
-C [min]

Collect garbage—i.e., unreachable /gnu/store files and sub-directories. This is the default operation when no option is specified.

When min is given, stop once min bytes have been collected. min may be a number of bytes, or it may include a unit as a suffix, such as MiB for mebibytes and GB for gigabytes.

When min is omitted, collect all the garbage.

--delete
-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.

--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.

--list-live

Show the list of live store files and directories.

In addition, the references among existing store files can be queried:

--references
--referrers

List the references (respectively, the referrers) of store files given as arguments.

--requisites
-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 transitive closure of the store files.


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3.6 Invoking 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 guix pull: the command downloads the latest Guix source code and package descriptions, and deploys it.

On completion, 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 guix sub-commands added by the update also become available.

The guix pull command is usually invoked with no arguments, but it supports the following options:

--verbose

Produce verbose output, writing build logs to the standard error output.

--url=url

Download the source tarball of Guix from url.

By default, the tarball is taken from its canonical address at gnu.org, for the stable branch of Guix.

--bootstrap

Use the bootstrap Guile to build the latest Guix. This option is only useful to Guix developers.


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3.7 Invoking guix archive

The guix archive command allows users to export files from the store into a single archive, and to later import them. In particular, it allows store files to be transferred from one machine to another machine’s store. For example, to transfer the emacs package to a machine connected over SSH, one would run:

guix archive --export emacs | ssh the-machine guix archive --import

However, note that, in this example, all of emacs and its dependencies are transferred, regardless of what is already available in the target machine’s store. The --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.

The main options are:

--export

Export the specified store files or packages (see below.) Write the resulting archive to the standard output.

--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 --authorize below.)

--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.

--generate-key[=parameters]

Generate a new key pair for the daemons. This is a prerequisite before archives can be exported with --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 /etc/guix, in signing-key.pub (public key) and signing-key.sec (private key, which must be kept secret.) When parameters is omitted, it is a 4096-bit RSA key. Alternately, parameters can specify genkey parameters suitable for Libgcrypt (see gcry_pk_genkey in The Libgcrypt Reference Manual).

--authorize

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 signing-key.pub file.

The list of authorized keys is kept in the human-editable file /etc/guix/acl. The file contains “advanced-format s-expressions” and is structured as an access-control list in the Simple Public-Key Infrastructure (SPKI).

To export store files as an archive to the standard output, run:

guix archive --export options specifications...

specifications may be either store file names or package specifications, as for guix package (see Invoking guix package). For instance, the following command creates an archive containing the gui output of the git package and the main output of emacs:

guix archive --export git:gui /gnu/store/...-emacs-24.3 > great.nar

If the specified packages are not built yet, guix archive automatically builds them. The build process may be controlled with the same options that can be passed to the guix build command (see common build options).


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4 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 /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.

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 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 derive from them.

This chapter describes all these APIs in turn, starting from high-level package definitions.


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4.1 Defining Packages

The high-level interface to package definitions is implemented in the (guix packages) and (guix build-system) modules. As an example, the package definition, or recipe, for the GNU Hello package looks like this:

(define-module (gnu packages hello)
  #:use-module (guix packages)
  #:use-module (guix download)
  #:use-module (guix build-system gnu)
  #:use-module (guix licenses))

(define 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+)))

Without being a Scheme expert, the reader may have guessed the meaning of the various fields here. This expression binds variable hello to a <package> object, which is essentially a record (see Scheme records in GNU Guile Reference Manual). This package object can be inspected using procedures found in the (guix packages) module; for instance, (package-name hello) returns—surprise!—"hello".

In the example above, hello is defined into a module of its own, (gnu packages hello). Technically, this is not strictly necessary, but it is convenient to do so: all the packages defined in modules under (gnu packages …) are automatically known to the command-line tools (see Package Modules).

There are a few points worth noting in the above package definition:

Once a package definition is in place3, the package may actually be built using the guix build command-line tool (see Invoking guix build). See Packaging Guidelines, for more information on how to test package definitions.

Eventually, updating the package definition to a new upstream version can be partly automated by the guix refresh command (see Invoking guix refresh).

Behind the scenes, a derivation corresponding to the <package> object is first computed by the package-derivation procedure. That derivation is stored in a .drv file under /gnu/store. The build actions it prescribes may then be realized by using the build-derivations procedure (see The Store).

Scheme Procedure: package-derivation store package [system]

Return the <derivation> object of package for system (see Derivations).

package must be a valid <package> object, and system must be a string denoting the target system type—e.g., "x86_64-linux" for an x86_64 Linux-based GNU system. store must be a connection to the daemon, which operates on the store (see The Store).

Similarly, it is possible to compute a derivation that cross-builds a package for some other system:

Scheme Procedure: package-cross-derivation store package target [system]

Return the <derivation> object of package cross-built from system to target.

target must be a valid GNU triplet denoting the target hardware and operating system, such as "mips64el-linux-gnu" (see GNU configuration triplets in GNU Configure and Build System).


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4.2 Build Systems

Each package definition specifies a build system and arguments for that build system (see Defining Packages). This build-system field represents the build procedure of the package, as well implicit dependencies of that build procedure.

Build systems are <build-system> objects. The interface to create and manipulate them is provided by the (guix build-system) module, and actual build systems are exported by specific modules.

Build systems accept an optional list of arguments. In package definitions, these are passed via the arguments field (see Defining Packages). They are typically keyword arguments (see keyword arguments in Guile in GNU Guile Reference Manual). The value of these arguments is usually evaluated in the build stratum—i.e., by a Guile process launched by the daemon (see Derivations).

The main build system is gnu-build-system, which implements the standard build procedure for GNU packages and many other packages. It is provided by the (guix build-system gnu) module.

Scheme Variable: gnu-build-system

gnu-build-system represents the GNU Build System, and variants thereof (see configuration and makefile conventions in GNU Coding Standards).

In a nutshell, packages using it configured, built, and installed with the usual ./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 phases, notably4:

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.

patch-source-shebangs

Patch shebangs encountered in source files so they refer to the right store file names. For instance, this changes #!/bin/sh to #!/gnu/store/…-bash-4.3/bin/sh.

configure

Run the configure script with a number of default options, such as --prefix=/gnu/store/…, as well as the options specified by the #:configure-flags argument.

build

Run make with the list of flags specified with #:make-flags. If the #:parallel-builds? argument is true (the default), build with make -j.

check

Run make check, or some other target specified with #:test-target, unless #:tests? #f is passed. If the #:parallel-tests? argument is true (the default), run make check -j.

install

Run make install with the flags listed in #:make-flags.

patch-shebangs

Patch shebangs on the installed executable files.

strip

Strip debugging symbols from ELF files (unless #:strip-binaries? is false), copying them to the debug output when available (see Installing Debugging Files).

The build-side module (guix build gnu-build-system) defines %standard-phases as the default list of build phases. %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 #:phases parameter. For instance, passing:

#:phases (alist-delete 'configure %standard-phases)

means that all the phases described above will be used, except the 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 (guix build-system gnu) module for a complete list.) We call these the implicit inputs of a package, because package definitions don’t have to mention them.

Other <build-system> objects are defined to support other conventions and tools used by free software packages. They inherit most of 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.

Scheme Variable: cmake-build-system

This variable is exported by (guix build-system cmake). It implements the build procedure for packages using the CMake build tool.

It automatically adds the cmake package to the set of inputs. Which package is used can be specified with the #:cmake parameter.

Scheme Variable: python-build-system

This variable is exported by (guix build-system python). It implements the more or less standard build procedure used by Python packages, which consists in running python setup.py build and then python setup.py install --prefix=/gnu/store/….

For packages that install stand-alone Python programs under bin/, it takes care of wrapping these programs so their PYTHONPATH environment variable points to all the Python libraries they depend on.

Which Python package is used can be specified with the #:python parameter.

Scheme Variable: perl-build-system

This variable is exported by (guix build-system perl). It implements the standard build procedure for Perl packages, which consists in running perl Makefile.PL PREFIX=/gnu/store/…, followed by make and make install.

The initial perl Makefile.PL invocation passes flags specified by the #:make-maker-flags parameter.

Which Perl package is used can be specified with #:perl.

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.

Scheme Variable: trivial-build-system

This variable is exported by (guix build-system trivial).

This build system requires a #:builder argument. This argument must be a Scheme expression that builds the package’s output(s)—as with build-expression->derivation (see build-expression->derivation).


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4.3 The Store

Conceptually, the store is where derivations that have been successfully built are stored—by default, under /gnu/store. Sub-directories in the store are referred to as 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 valid store paths—paths that result from a successful build.

The store is always accessed by the daemon on behalf of its clients (see 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 (guix store) module provides procedures to connect to the daemon, and to perform RPCs. These are described below.

Scheme Procedure: open-connection [file] [#:reserve-space? #t]

Connect to the daemon over the Unix-domain socket at file. When 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.

file defaults to %default-socket-path, which is the normal location given the options that were passed to configure.

Scheme Procedure: close-connection server

Close the connection to server.

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.

Procedures that make RPCs all take a server object as their first argument.

Scheme Procedure: valid-path? server path

Return #t when path is a valid store path.

Scheme Procedure: add-text-to-store server name text [references]

Add text under file name in the store, and return its store path. references is the list of store paths referred to by the resulting store path.

Scheme Procedure: build-derivations server derivations

Build derivations (a list of <derivation> objects or derivation paths), and return when the worker is done building them. Return #t on success.

Note that the (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 (see The Store Monad).

This section is currently incomplete.


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4.4 Derivations

Low-level build actions and the environment in which they are performed are represented by derivations. A derivation contain the following pieces of information:

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 .drv—these files are referred to as derivation paths. Derivations paths can be passed to the build-derivations procedure to perform the build actions they prescribe (see The Store).

The (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 derivation procedure:

Scheme Procedure: derivation store name builder 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 <derivation> object.

When hash and hash-algo are given, a fixed-output derivation is created—i.e., one whose result is known in advance, such as a file download. If, in addition, recursive? is true, then that fixed output may be an executable file or a directory and hash must be the hash of an archive containing this output.

When 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 allowed-references is true, it must be a list of store items or outputs that the derivation’s output may refer to.

When local-build? is true, declare that the derivation is not a good candidate for offloading and should rather be built locally (see Daemon Offload Setup). This is the case for small derivations where the costs of data transfers would outweigh the benefits.

Here’s an example with a shell script as its builder, assuming store is an open connection to the daemon, and bash points to a Bash executable in the store:

(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"))))
⇒ #<derivation /gnu/store/…-foo.drv => /gnu/store/…-foo>

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 gexp->derivation. For more information, see G-Expressions.

Once upon a time, gexp->derivation did not exist and constructing derivations with build code written in Scheme was achieved with build-expression->derivation, documented below. This procedure is now deprecated in favor of the much nicer gexp->derivation.

Scheme Procedure: build-expression->derivation store name 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 exp as a builder for derivation name. inputs must be a list of (name drv-path sub-drv) tuples; when sub-drv is omitted, "out" is assumed. 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 exp—e.g., ((guix build utils) (guix build gnu-build-system)).

exp is evaluated in an environment where %outputs is bound to a list of output/path pairs, and where %build-inputs is bound to a list of string/output-path pairs made from inputs. Optionally, 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 exp to exit; thus, when exp returns #f, the build is considered to have failed.

exp is built using guile-for-build (a derivation). When guile-for-build is omitted or is #f, the value of the %guile-for-build fluid is used instead.

See the derivation procedure for the meaning of references-graphs, allowed-references, and local-build?.

Here’s an example of a single-output derivation that creates a directory containing one file:

(let ((builder '(let ((out (assoc-ref %outputs "out")))
                  (mkdir out)    ; create /gnu/store/…-goo
                  (call-with-output-file (string-append out "/test")
                    (lambda (p)
                      (display '(hello guix) p))))))
  (build-expression->derivation store "goo" builder))

⇒ #<derivation /gnu/store/…-goo.drv => …>

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4.5 The Store 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.

This is where the (guix monads) module comes in. This module provides a framework for working with monads, and a particularly useful monad for our uses, the 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 includes accesses to the store.) Values in a monad—values that carry this additional context—are called monadic values; procedures that return such values are called monadic procedures.

Consider this “normal” procedure:

(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))))

Using (guix monads), it may be rewritten as a monadic function:

(define (sh-symlink)
  ;; Same, but return a monadic value.
  (gexp->derivation "sh"
                    #~(symlink (string-append #$bash "/bin/bash") #$output)))

There are two things to note in the second version: the store parameter is now implicit, and the monadic value returned by package-file—a wrapper around package-derivation and derivation->output-path—is bound using mlet instead of plain let.

Calling the monadic profile.sh has no effect. To get the desired effect, one must use run-with-store:

(run-with-store (open-connection) (profile.sh))
⇒ /gnu/store/...-profile.sh

The main syntactic forms to deal with monads in general are described below.

Scheme Syntax: with-monad monad body ...

Evaluate any >>= or return forms in body as being in monad.

Scheme Syntax: return val

Return a monadic value that encapsulates val.

Scheme Syntax: >>= mval mproc

Bind monadic value mval, passing its “contents” to monadic procedure mproc5.

Scheme Syntax: mlet monad ((var mval) ...) body ...
Scheme Syntax: mlet* monad ((var mval) ...) body ...

Bind the variables var to the monadic values mval in body. The form (var -> val) binds var to the “normal” value val, as per let.

mlet* is to mlet what let* is to let (see Local Bindings in GNU Guile Reference Manual).

The interface to the store monad provided by (guix monads) is as follows.

Scheme Variable: %store-monad

The store 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 run-with-store procedure (see below.)

Scheme Procedure: run-with-store store mval [#:guile-for-build] [#:system (%current-system)]

Run mval, a monadic value in the store monad, in store, an open store connection.

Monadic Procedure: text-file name text

Return as a monadic value the absolute file name in the store of the file containing text, a string.

Monadic Procedure: text-file* name text

Return as a monadic value a derivation that builds a text file containing all of text. 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 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:

(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"))

In this example, the resulting /gnu/store/…-profile.sh file will references coreutils, grep, and sed, thereby preventing them from being garbage-collected during its lifetime.

Monadic Procedure: interned-file file [name] [#:recursive? #t]

Return the name of file once interned in the store. Use name as its store name, or the basename of file if name is omitted.

When recursive? is true, the contents of file are added recursively; if file designates a flat file and 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:

(run-with-store (open-connection)
  (mlet %store-monad ((a (interned-file "README"))
                      (b (interned-file "README" "LEGU-MIN")))
    (return (list a b))))

⇒ ("/gnu/store/rwm…-README" "/gnu/store/44i…-LEGU-MIN")
Monadic Procedure: package-file package [file] [#:system (%current-system)] [#:output "out"] Return as a monadic

value in the absolute file name of file within the output directory of package. When file is omitted, return the name of the output directory of package.

Monadic Procedure: package->derivation package [system]

Monadic version of package-derivation (see Defining Packages).


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4.6 G-Expressions

So we have “derivations”, which represent a sequence of build actions to be performed to produce an item in the store (see Derivations). Those build actions are performed when asking the daemon to actually build the derivations; they are run by the daemon in a container (see Invoking guix-daemon).

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 strata of Scheme code6: 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 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 quasiquote mechanism to construct build expressions.

The (guix gexp) module implements G-expressions, a form of S-expressions adapted to build expressions. G-expressions, or gexps, consist essentially in three syntactic forms: gexp, ungexp, and ungexp-splicing (or simply: #~, #$, and #$@), which are comparable respectively to quasiquote, unquote, and unquote-splicing (see quasiquote in GNU Guile Reference Manual). However, there are major differences:

To illustrate the idea, here is an example of a gexp:

(define build-exp
  #~(begin
      (mkdir #$output)
      (chdir #$output)
      (symlink (string-append #$coreutils "/bin/ls") 
               "list-files")))

This gexp can be passed to gexp->derivation; we obtain a derivation that builds a directory containing exactly one symlink to /gnu/store/…-coreutils-8.22/bin/ls:

(gexp->derivation "the-thing" build-exp)

As one would expect, the "/gnu/store/…-coreutils-8.22" string is substituted to the reference to the coreutils package in the actual build code, and coreutils is automatically made an input to the derivation. Likewise, #$output (equivalent to (ungexp output)) is replaced by a string containing the derivation’s output directory name. The syntactic form to construct gexps is summarized below.

Scheme Syntax: #~ exp
Scheme Syntax: (gexp exp)

Return a G-expression containing exp. exp may contain one or more of the following forms:

#$obj
(ungexp obj)

Introduce a reference to obj. obj may be a package or a derivation, in which case the ungexp form is replaced by its output file name—e.g., "/gnu/store/…-coreutils-8.22.

If obj is a list, it is traversed and any package or derivation references are substituted similarly.

If obj is another gexp, its contents are inserted and its dependencies are added to those of the containing gexp.

If obj is another kind of object, it is inserted as is.

#$package-or-derivation:output
(ungexp package-or-derivation output)

This is like the form above, but referring explicitly to the output of package-or-derivation—this is useful when package-or-derivation produces multiple outputs (see Packages with Multiple Outputs).

#$output[:output]
(ungexp output [output])

Insert a reference to derivation output output, or to the main output when output is omitted.

This only makes sense for gexps passed to gexp->derivation.

#$@lst
(ungexp-splicing lst)

Like the above, but splices the contents of lst inside the containing list.

G-expressions created by gexp or #~ are run-time objects of the gexp? type (see below.)

Scheme Procedure: gexp? obj

Return #t if obj is a G-expression.

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 (see The Store Monad, for more information about monads.)

Monadic Procedure: gexp->derivation name exp [#:system (%current-system)] [#:inputs '()] [#:hash #f] [#:hash-algo #f] [#:recursive? #f] [#:env-vars '()] [#:modules '()] [#:references-graphs #f] [#:local-build? #f] [#:guile-for-build #f]

Return a derivation name that runs exp (a gexp) with guile-for-build (a derivation) on system.

Make modules available in the evaluation context of EXP; 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 exp—e.g., ((guix build utils) (guix build gnu-build-system)).

The other arguments are as for derivation (see Derivations).

Monadic Procedure: gexp->script name exp

Return an executable script name that runs exp using guile with modules in its search path.

The example below builds a script that simply invokes the ls command:

(use-modules (guix gexp) (gnu packages base))

(gexp->script "list-files"
              #~(execl (string-append #$coreutils "/bin/ls")
                       "ls"))

When “running” it through the store (see run-with-store), we obtain a derivation that produces an executable file /gnu/store/…-list-files along these lines:

#!/gnu/store/…-guile-2.0.11/bin/guile -ds
!#
(execl (string-append "/gnu/store/…-coreutils-8.22"/bin/ls")
       "ls")
Monadic Procedure: gexp->file name exp

Return a derivation that builds a file name containing exp.

The resulting file holds references to all the dependencies of exp or a subset thereof.

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 (guix build …) name space.


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5 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.


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5.1 Invoking guix build

The 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 guix package command (see Invoking guix package). Thus, it is mainly useful for distribution developers.

The general syntax is:

guix build options package-or-derivation

package-or-derivation may be either the name of a package found in the software distribution such as coreutils or coreutils-8.20, or a derivation such as /gnu/store/…-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 (see Package Modules).

Alternatively, the --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 options may be zero or more of the following:

--expression=expr
-e expr

Build the package or derivation expr evaluates to.

For example, expr may be (@ (gnu packages guile) guile-1.8), which unambiguously designates this specific variant of version 1.8 of Guile.

Alternately, expr may be a G-expression, in which case it is used as a build program passed to gexp->derivation (see G-Expressions).

Lastly, expr may refer to a zero-argument monadic procedure (see The Store Monad). The procedure must return a derivation as a monadic value, which is then passed through run-with-store.

--source
-S

Build the packages’ source derivations, rather than the packages themselves.

For instance, guix build -S gcc returns something like /gnu/store/…-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 origin (see Defining Packages).

--system=system
-s system

Attempt to build for system—e.g., 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 --system=i686-linux on an x86_64-linux system allows users to build packages in a complete 32-bit environment.

--target=triplet

Cross-build for triplet, which must be a valid GNU triplet, such as "mips64el-linux-gnu" (see GNU configuration triplets in GNU Configure and Build System).

--with-source=source

Use source as the source of the corresponding package. source must be a file name or a URL, as for guix download (see Invoking guix download).

The “corresponding package” is taken to be one specified on the command line whose name matches the base of source—e.g., if source is /src/guile-2.0.10.tar.gz, the corresponding package is guile. Likewise, the version string is inferred from source; in the previous example, it’s 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 ed-1.7.tar.gz from a GNU mirror and uses that as the source for the ed package:

guix build ed --with-source=mirror://gnu/ed/ed-1.7.tar.gz

As a developer, --with-source makes it easy to test release candidates:

guix build guile --with-source=../guile-2.0.9.219-e1bb7.tar.xz
--derivations
-d

Return the derivation paths, not the output paths, of the given packages.

--root=file
-r file

Make file a symlink to the result, and register it as a garbage collector root.

--log-file

Return the build log file names for the given package-or-derivations, 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:

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)'

In addition, a number of options that control the build process are common to guix build and other commands that can spawn builds, such as guix package or guix archive. These are the following:

--keep-failed
-K

Keep the build tree of failed builds. Thus, if a build fail, its build tree is kept under /tmp, in a directory whose name is shown at the end of the build log. This is useful when debugging build issues.

--dry-run
-n

Do not build the derivations.

--fallback

When substituting a pre-built binary fails, fall back to building packages locally.

--no-substitutes

Do not use substitutes for build products. That is, always build things locally instead of allowing downloads of pre-built binaries (see Substitutes).

--no-build-hook

Do not attempt to offload builds via the daemon’s “build hook” (see Daemon Offload Setup). That is, always build things locally instead of offloading builds to remote machines.

--max-silent-time=seconds

When the build or substitution process remains silent for more than seconds, terminate it and report a build failure.

--timeout=seconds

Likewise, when the build or substitution process lasts for more than seconds, terminate it and report a build failure.

By default there is no timeout. This behavior can be restored with --timeout=0.

--verbosity=level

Use the given verbosity level. 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.

--cores=n
-c n

Allow the use of up to n CPU cores for the build. The special value 0 means to use as many CPU cores as available.

Behind the scenes, guix build is essentially an interface to the package-derivation procedure of the (guix packages) module, and to the build-derivations procedure of the (guix store) module.


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5.2 Invoking 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 (see Defining Packages). The 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 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 (see Invoking guix gc).

The guix download command supports the same URIs as used in package definitions. In particular, it supports mirror:// URIs. https URIs (HTTP over TLS) are supported provided the Guile bindings for GnuTLS are available in the user’s environment; when they are not available, an error is raised.

The following option is available:

--format=fmt
-f fmt

Write the hash in the format specified by fmt. For more information on the valid values for fmt, Invoking guix hash.


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5.3 Invoking guix hash

The 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 (see Defining Packages).

The general syntax is:

guix hash option file

guix hash has the following option:

--format=fmt
-f fmt

Write the hash in the format specified by fmt.

Supported formats: nix-base32, base32, base16 (hex and hexadecimal can be used as well).

If the --format option is not specified, guix hash will output the hash in nix-base32. This representation is used in the definitions of packages.

--recursive
-r

Compute the hash on file recursively.

In this case, the hash is computed on an archive containing file, including its children if it is a directory. Some of file’s meta-data is part of the archive; for instance, when file is a regular file, the hash is different depending on whether file is executable or not. Meta-data such as time stamps has no impact on the hash (see Invoking guix archive).


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5.4 Invoking guix refresh

The primary audience of the 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:

$ 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

It does so by browsing each package’s FTP directory and determining the highest version number of the source tarballs therein7.

When passed --update, it modifies distribution source files to update the version numbers and source tarball hashes of those packages’ recipes (see 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 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, guix refresh reports an error.

The following options are supported:

--update
-u

Update distribution source files (package recipes) in place. Defining Packages, for more information on package definitions.

--select=[subset]
-s subset

Select all the packages in subset, one of core or non-core.

The 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 non-core subset refers to the remaining packages. It is typically useful in cases where an update of the core packages would be inconvenient.

In addition, guix refresh can be passed one or more package names, as in this example:

guix refresh -u emacs idutils

The command above specifically updates the emacs and idutils packages. The --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 guix refresh one or more package names:

--list-dependent
-l

List top-level dependent packages that would need to be rebuilt as a result of upgrading one or more packages.

Be aware that the --list-dependent option only approximates the rebuilds that would be required as a result of an upgrade. More rebuilds might be required under some circumstances.

$ 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 …

The command above lists a set of packages that could be built to check for compatibility with an upgraded flex package.

The following options can be used to customize GnuPG operation:

--key-server=host

Use host as the OpenPGP key server when importing a public key.

--gpg=command

Use command as the GnuPG 2.x command. command is searched for in $PATH.


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6 GNU Distribution

Guix comes with a distribution of free software8 that forms the basis of the GNU system. This includes 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 on-line or by running guix package (see Invoking guix package):

guix package --list-available

Our goal is to build 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.

The GNU distribution is currently available on the following platforms:

x86_64-linux

Intel/AMD x86_64 architecture, Linux-Libre kernel;

i686-linux

Intel 32-bit architecture (IA32), Linux-Libre kernel;

mips64el-linux

little-endian 64-bit MIPS processors, specifically the Loongson series, n32 application binary interface (ABI), and Linux-Libre kernel.

For information on porting to other architectures or kernels, See Porting.

Building this distribution is a cooperative effort, and you are invited to join! Contributing, for information about how you can help.


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6.1 System Installation

This section explains how to install the complete GNU operating system on a machine. The Guix package manager can also be installed on top of a running GNU/Linux system, see Installation.

6.1.1 Limitations

As of version 0.7, GNU Guix and the GNU system distribution are alpha software. 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 one of more established GNU/Linux distributions. We hope you can soon switch to the GNU system without fear, of course. In the meantime, you can also keep using your distribution and try out the package manager on top of it (see Installation).

Before you proceed with the installation, be aware of the following noteworthy limitations applicable to version 0.7:

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. See Contributing, for more info.

6.1.2 USB Stick Installation

An installation image for USB sticks can be downloaded from ftp://alpha.gnu.org/gnu/guix/gnu-usb-install-0.7.system.xz, where system is one of:

x86_64-linux

for a GNU/Linux system on Intel/AMD-compatible 64-bit CPUs;

i686-linux

for a 32-bit GNU/Linux system on Intel-compatible CPUs.

This image contains a single partition with the tools necessary for an installation. It is meant to be copied as is to a large-enough USB stick.

To copy the image to a USB stick, follow these steps:

  1. Decompress the image using the xz command:
    xz -d gnu-usb-install-0.7.system.xz
    
  2. Insert a USB stick of 1 GiB or more in your machine, and determine its device name. Assuming that USB stick is known as /dev/sdX, copy the image with:
    dd if=gnu-usb-install-0.7.x86_64 of=/dev/sdX
    

    Access to /dev/sdX usually requires root privileges.

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.

6.1.3 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 (see Help in Info: An Introduction).

To install the system, you would:

  1. Configure the network, by running dhclient eth0 (to get an automatically assigned IP address from the wired network interface controller), or using the 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.

  2. 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 file-system declarations (see File Systems). This is typically done using the -L option of mkfs.ext4 and related commands.

    The installation image includes Parted (see Overview in GNU Parted User Manual), fdisk, and e2fsprogs, the suite of tools to manipulate ext2/ext3/ext4 file systems.

  3. Once that is done, mount the target root partition under /mnt.
  4. Lastly, run deco start cow-store /mnt.

    This will make /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.

6.1.4 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 (see GNU nano Manual), and GNU Zile, an Emacs clone. It is better to store that file on the target root file system, say, as /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 /etc/configuration-template.scm):

;; This is an operating system configuration template.

(use-modules (gnu))

(operating-system
  (host-name "antelope")
  (timezone "Europe/Paris")
  (locale "en_US.UTF-8")

  ;; Assuming /dev/sdX is the target hard disk, and "root" is
  ;; the label of the target root file system.
  (bootloader (grub-configuration (device "/dev/sdX")))
  (file-systems (cons (file-system
                        (device "root")
                        (title 'label)
                        (mount-point "/")
                        (type "ext4"))
                      %base-file-systems))

  ;; This is where user accounts are specified.  The "root"
  ;; account is implicit, and is initially created with the
  ;; empty password.
  (users (list (user-account
                (name "alice")
                (comment "Bob's sister")
                (group "users")

                ;; Adding the account to the "wheel" group
                ;; makes it a sudoer.
                (supplementary-groups '("wheel"))
                (home-directory "/home/alice")))))

For more information on operating-system declarations, see Using the Configuration System.

Once that is done, the new system must be initialized (remember that the target root file system is mounted under /mnt):

guix system init /mnt/etc/config.scm /mnt

This will copy all the necessary files, and install GRUB on /dev/sdX, unless you pass the --no-grub option. For more information, see Invoking guix system. This command may trigger downloads or builds of missing packages, which can take some time.

Once that command has completed—and hopefully succeeded!—you can unmount /mnt and boot into the new system. Cross fingers, and join us on #guix on the Freenode IRC network or on guix-devel@gnu.org to share your experience—good or not so good.

6.1.5 Building the Installation Image

The installation image described above was built using the guix system command, specifically:

guix system disk-image --image-size=800MiB gnu/system/install.scm

See Invoking guix system, for more information. See gnu/system/install.scm in the source tree for more information about the installation image.


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6.2 System Configuration

The GNU system supports a consistent whole-system configuration mechanism. By that we mean that all aspects of the global system configuration—such as the available system services, timezone and locale settings, user accounts—are declared in a single place. Such a system configuration can be instantiated—i.e., effected.

One of the advantages of putting all the system configuration under the control of Guix is that it supports transactional system upgrades, and makes it possible to roll-back to a previous system instantiation, should something go wrong with the new one (see Features). Another one is that it makes it easy to replicate the exact same configuration across different machines, or at different points in time, without having to resort to additional administration tools layered on top of the system’s own tools.

This section describes this mechanism. First we focus on the system administrator’s viewpoint—explaining how the system is configured and instantiated. Then we show how this mechanism can be extended, for instance to support new system services.


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6.2.1 Using the Configuration System

The operating system is configured by providing an operating-system declaration in a file that can then be passed to the guix system command (see Invoking guix system). A simple setup, with the default system services, the default Linux-Libre kernel, initial RAM disk, and boot loader looks like this:

(use-modules (gnu)   ; for 'user-account', '%base-services', etc.
             (gnu packages emacs)  ; for 'emacs'
             (gnu services ssh))   ; for 'lsh-service'

(operating-system
  (host-name "komputilo")
  (timezone "Europe/Paris")
  (locale "fr_FR.UTF-8")
  (bootloader (grub-configuration
                (device "/dev/sda")))
  (file-systems (cons (file-system
                        (device "/dev/sda1") ; or partition label
                        (mount-point "/")
                        (type "ext3"))
                      %base-file-systems))
  (users (list (user-account
                (name "alice")
                (password "")
                (uid 1000) (group 100)
                (comment "Bob's sister")
                (home-directory "/home/alice"))))
  (packages (cons emacs %base-packages))
  (services (cons (lsh-service #:port 2222 #:allow-root-login? #t)
                  %base-services)))

This example should be self-describing. Some of the fields defined above, such as host-name and bootloader, are mandatory. Others, such as packages and services, can be omitted, in which case they get a default value.

The packages field lists packages that will be globally visible on the system, for all user accounts—i.e., in every user’s PATH environment variable—in addition to the per-user profiles (see Invoking guix package). The %base-packages variable provides all the tools one would expect for basic user and administrator tasks—including the GNU Core Utilities, the GNU Networking Utilities, the GNU Zile lightweight text editor, find, grep, etc. The example above adds Emacs to those, taken from the (gnu packages emacs) module (see Package Modules).

The services field lists system services to be made available when the system starts (see Services). The operating-system declaration above specifies that, in addition to the basic services, we want the lshd secure shell daemon listening on port 2222, and allowing remote root logins (see Invoking lshd in GNU lsh Manual). Under the hood, lsh-service arranges so that lshd is started with the right command-line options, possibly with supporting configuration files generated as needed (see Defining Services).

Assuming the above snippet is stored in the my-system-config.scm file, the guix system reconfigure my-system-config.scm command instantiates that configuration, and makes it the default GRUB boot entry (see Invoking guix system). The normal way to change the system’s configuration is by updating this file and re-running the guix system command.

At the Scheme level, the bulk of an operating-system declaration is instantiated with the following monadic procedure (see The Store Monad):

Monadic Procedure: operating-system-derivation os

Return a derivation that builds os, an operating-system object (see Derivations).

The output of the derivation is a single directory that refers to all the packages, configuration files, and other supporting files needed to instantiate os.


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6.2.2 File Systems

The list of file systems to be mounted is specified in the file-systems field of the operating system’s declaration (see Using the Configuration System). Each file system is declared using the file-system form, like this:

(file-system
  (mount-point "/home")
  (device "/dev/sda3")
  (type "ext4"))

As usual, some of the fields are mandatory—those shown in the example above—while others can be omitted. These are described below.

Data Type: file-system

Objects of this type represent file systems to be mounted. They contain the following members:

type

This is a string specifying the type of the file system—e.g., "ext4".

mount-point

This designates the place where the file system is to be mounted.

device

This names the “source” of the file system. By default it is the name of a node under /dev, but its meaning depends on the title field described below.

title (default: 'device)

This is a symbol that specifies how the device field is to be interpreted.

When it is the symbol device, then the device field is interpreted as a file name; when it is label, then device is interpreted as a partition label name; when it is uuid, device is interpreted as a partition unique identifier (UUID).

The label and uuid options offer a way to refer to disk partitions without having to hard-code their actual device name.

flags (default: '())

This is a list of symbols denoting mount flags. Recognized flags include read-only, bind-mount, no-dev (disallow access to special files), no-suid (ignore setuid and setgid bits), and no-exec (disallow program execution.)

options (default: #f)

This is either #f, or a string denoting mount options.

needed-for-boot? (default: #f)

This Boolean value indicates whether the file system is needed when booting. If that is true, then the file system is mounted when the initial RAM disk (initrd) is loaded. This is always the case, for instance, for the root file system.

check? (default: #t)

This Boolean indicates whether the file system needs to be checked for errors before being mounted.

create-mount-point? (default: #f)

When true, the mount point is created if it does not exist yet.

The (gnu system file-systems) exports the following useful variables.

Scheme Variable: %base-file-systems

These are essential file systems that are required on normal systems, such as %devtmpfs-file-system (see below.) Operating system declarations should always contain at least these.

Scheme Variable: %devtmpfs-file-system

The devtmpfs file system to be mounted on /dev. This is a requirement for udev (see udev-service).

Scheme Variable: %pseudo-terminal-file-system

This is the file system to be mounted as /dev/pts. It supports pseudo-terminals created via openpty and similar functions (see Pseudo-Terminals in The GNU C Library Reference Manual). Pseudo-terminals are used by terminal emulators such as xterm.

Scheme Variable: %shared-memory-file-system

This file system is mounted as /dev/shm and is used to support memory sharing across processes (see shm_open in The GNU C Library Reference Manual).

Scheme Variable: %binary-format-file-system

The binfmt_misc file system, which allows handling of arbitrary executable file types to be delegated to user space. This requires the binfmt.ko kernel module to be loaded.

Scheme Variable: %fuse-control-file-system

The fusectl file system, which allows unprivileged users to mount and unmount user-space FUSE file systems. This requires the fuse.ko kernel module to be loaded.


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6.2.3 User Accounts

User accounts are specified with the user-account form:

(user-account
  (name "alice")
  (group "users")
  (supplementary-groups '("wheel"))  ; allow use of sudo, etc.
  (comment "Bob's sister")
  (home-directory "/home/alice"))
Data Type: user-account

Objects of this type represent user accounts. The following members may be specified:

name

The name of the user account.

group

This is the name (a string) or identifier (a number) of the user group this account belongs to.

supplementary-groups (default: '())

Optionally, this can be defined as a list of group names that this account belongs to.

uid (default: #f)

This is the user ID for this account (a number), or #f. In the latter case, a number is automatically chosen by the system when the account is created.

comment (default: "")

A comment about the account, such as the account’s owner full name.

home-directory

This is the name of the home directory for the account.

shell (default: Bash)

This is a G-expression denoting the file name of a program to be used as the shell (see G-Expressions).

system? (default: #f)

This Boolean value indicates whether the account is a “system” account. System accounts are sometimes treated specially; for instance, graphical login managers do not list them.

password (default: #f)

Unless #f, this is the password to be used for the account.

User group declarations are even simpler:

(user-group (name "students"))
Data Type: user-group

This type is for, well, user groups. There are just a few fields:

name

The group’s name.

id (default: #f)

The group identifier (a number). If #f, a new number is automatically allocated when the group is created.

system? (default: #f)

This Boolean value indicates whether the group is a “system” group. System groups have low numerical IDs.

password (default: #f)

What, user groups can have a password? Well, apparently yes. Unless #f, this field specifies the group’s password.

For convenience, a variable lists all the basic user groups one may expect:

Scheme Variable: %base-groups

This is the list of basic user groups that users and/or packages expect to be present on the system. This includes groups such as “root”, “wheel”, and “users”, as well as groups used to control access to specific devices such as “audio”, “disk”, and “cdrom”.


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6.2.4 Services

An important part of preparing an operating-system declaration is listing system services and their configuration (see Using the Configuration System). System services are typically daemons launched when the system boots, or other actions needed at that time—e.g., configuring network access. They are managed by GNU dmd (see Introduction in GNU dmd Manual).

The following sections document the available services, starting with the core services.


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6.2.4.1 Base Services

The (gnu services base) module provides definitions for the basic services that one expects from the system. The services exported by this module are listed below.

Scheme Variable: %base-services

This variable contains a list of basic services9 one would expect from the system: a login service (mingetty) on each tty, syslogd, libc’s name service cache daemon (nscd), the udev device manager, and more.

This is the default value of the services field of operating-system declarations. Usually, when customizing a system, you will want to append services to %base-services, like this:

(cons* (avahi-service) (lshd-service) %base-services)
Monadic Procedure: host-name-service name

Return a service that sets the host name to name.

Monadic Procedure: mingetty-service tty [#:motd] [#:auto-login #f] [#:login-program] [#:login-pause? #f] [#:allow-empty-passwords? #f]

Return a service to run mingetty on tty.

When allow-empty-passwords? is true, allow empty log-in password. When auto-login is true, it must be a user name under which to log-in automatically. login-pause? can be set to #t in conjunction with auto-login, in which case the user will have to press a key before the login shell is launched.

When true, login-program is a gexp or a monadic gexp denoting the name of the log-in program (the default is the login program from the Shadow tool suite.)

motd is a monadic value containing a text file to use as the “message of the day”.

Monadic Procedure: nscd-service [#:glibc glibc]

Return a service that runs libc’s name service cache daemon (nscd).

Monadic Procedure: syslog-service

Return a service that runs syslogd with reasonable default settings.

Monadic Procedure: guix-service [#:guix guix] [#:builder-group "guixbuild"] [#:build-accounts 10] [#:authorize-hydra-key? #f] [#:use-substitutes? #t] [#:extra-options '()]

Return a service that runs the build daemon from guix, and has build-accounts user accounts available under builder-group.

When authorize-hydra-key? is true, the hydra.gnu.org public key provided by guix is authorized upon activation, meaning that substitutes from hydra.gnu.org are used by default.

If use-substitutes? is false, the daemon is run with --no-substitutes (see --no-substitutes).

Finally, extra-options is a list of additional command-line options passed to guix-daemon.

Monadic Procedure: udev-service [#:udev udev]

Run udev, which populates the /dev directory dynamically.


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6.2.4.2 Networking Services

The (gnu system networking) module provides services to configure the network interface.

Monadic Procedure: static-networking-service interface ip [#:gateway #f] [#:name-services '()]

Return a service that starts interface with address ip. If gateway is true, it must be a string specifying the default network gateway.

Monadic Procedure: tor-service [#:tor tor]

Return a service to run the Tor daemon.

The daemon runs with the default settings (in particular the default exit policy) as the tor unprivileged user.

In addition, (gnu system ssh) provides the following service.

Monadic Procedure: lsh-service [#:host-key "/etc/lsh/host-key"] [#:interfaces '()] [#:port-number 22] [#:allow-empty-passwords? #f] [#:root-login? #f] [#:syslog-output? #t] [#:x11-forwarding? #t] [#:tcp/ip-forwarding? #t] [#:password-authentication? #t] [public-key-authentication? #t] [#:initialize? #f]

Run the lshd program from lsh to listen on port port-number. host-key must designate a file containing the host key, and readable only by root.

When initialize? is true, automatically create the seed and host key upon service activation if they do not exist yet. This may take long and require interaction.

When interfaces is empty, lshd listens for connections on all the network interfaces; otherwise, interfaces must be a list of host names or addresses.

allow-empty-passwords? specifies whether to accepts log-ins with empty passwords, and root-login? specifies whether to accepts log-ins as root.

The other options should be self-descriptive.


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6.2.4.3 X Window

Support for the X Window graphical display system—specifically Xorg—is provided by the (gnu services xorg) module. Note that there is no xorg-service procedure. Instead, the X server is started by the login manager, currently SLiM.

Monadic Procedure: slim-service [#:allow-empty-passwords? #f] [#:auto-login? #f] [#:default-user ""] [#:startx]

Return a service that spawns the SLiM graphical login manager, which in turn starts the X display server with startx, a command as returned by xorg-start-command.

When allow-empty-passwords? is true, allow logins with an empty password. When auto-login? is true, log in automatically as default-user.


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6.2.5 Setuid Programs

Some programs need to run with “root” privileges, even when they are launched by unprivileged users. A notorious example is the passwd programs, which can users can run to change their password, and which requires write access to the /etc/passwd and /etc/shadow files—something normally restricted to root, for obvious security reasons. To address that, these executables are setuid-root, meaning that they always run with root privileges (see How Change Persona in The GNU C Library Reference Manual, for more info about the setuid mechanisms.)

The store itself cannot contain setuid programs: that would be a security issue since any user on the system can write derivations that populate the store (see The Store). Thus, a different mechanism is used: instead of changing the setuid bit directly on files that are in the store, we let the system administrator declare which programs should be setuid root.

The setuid-programs field of an operating-system declaration contains a list of G-expressions denoting the names of programs to be setuid-root (see Using the Configuration System). For instance, the passwd program, which is part of the Shadow package, can be designated by this G-expression (see G-Expressions):

#~(string-append #$shadow "/bin/passwd")

A default set of setuid programs is defined by the %setuid-programs variable of the (gnu system) module.

Scheme Variable: %setuid-programs

A list of G-expressions denoting common programs that are setuid-root.

The list includes commands such as passwd, ping, su, and sudo.

Under the hood, the actual setuid programs are created in the /run/setuid-programs directory at system activation time. The files in this directory refer to the “real” binaries, which are in the store.


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6.2.6 Initial RAM Disk

For bootstrapping purposes, the Linux-Libre kernel is passed an initial RAM disk, or initrd. An initrd contains a temporary root file system, as well as an initialization script. The latter is responsible for mounting the real root file system, and for loading any kernel modules that may be needed to achieve that.

The initrd field of an operating-system declaration allows you to specify which initrd you would like to use. The (gnu system linux-initrd) module provides two ways to build an initrd: the high-level base-initrd procedure, and the low-level expression->initrd procedure.

The base-initrd procedure is intended to cover most common uses. For example, if you want to add a bunch of kernel modules to be loaded at boot time, you can define the initrd field of the operating system declaration like this:

(initrd (cut base-initrd <>
             #:extra-modules '("my.ko" "modules.ko")))

It also handles common use cases that involves using the system as a QEMU guest, or as a “live” system whose root file system is volatile.

Monadic Procedure: base-initrd file-systems [#:qemu-networking? #f] [#:virtio? #f] [#:volatile-root? #f] [#:extra-modules '()]

Return a monadic derivation that builds a generic initrd. file-systems is a list of file-systems to be mounted by the initrd, possibly in addition to the root file system specified on the kernel command line via --root.

When qemu-networking? is true, set up networking with the standard QEMU parameters. When virtio? is true, load additional modules so the initrd can be used as a QEMU guest with para-virtualized I/O drivers.

When volatile-root? is true, the root file system is writable but any changes to it are lost.

The initrd is automatically populated with all the kernel modules necessary for file-systems and for the given options. However, additional kernel modules can be listed in extra-modules. They will be added to the initrd, and loaded at boot time in the order in which they appear.

Needless to say, the initrds we produce and use embed a statically-linked Guile, and the initialization program is a Guile program. That gives a lot of flexibility. The expression->initrd procedure builds such an initrd, given the program to run in that initrd.

Monadic Procedure: expression->initrd exp [#:guile %guile-static-stripped] [#:name "guile-initrd"] [#:modules '()] [#:to-copy '()] [#:linux #f] [#:linux-modules '()]

Return a derivation that builds a Linux initrd (a gzipped cpio archive) containing guile and that evaluates exp, a G-expression, upon booting.

linux-modules is a list of .ko file names to be copied from linux into the initrd. to-copy is a list of additional derivations or packages to copy to the initrd. modules is a list of Guile module names to be embedded in the initrd.


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6.2.7 Invoking guix system

Once you have written an operating system declaration, as seen in the previous section, it can be instantiated using the guix system command. The synopsis is:

guix system optionsaction file

file must be the name of a file containing an operating-system declaration. action specifies how the operating system is instantiate. Currently the following values are supported:

reconfigure

Build the operating system described in file, activate it, and switch to it10.

This effects all the configuration specified in file: user accounts, system services, global package list, setuid programs, etc.

It also adds a GRUB menu entry for the new OS configuration, and moves entries for older configurations to a submenu—unless --no-grub is passed.

build

Build the operating system’s derivation, which includes all the configuration files and programs needed to boot and run the system. This action does not actually install anything.

init

Populate the given directory with all the files necessary to run the operating system specified in file. This is useful for first-time installations of the GNU system. For instance:

guix system init my-os-config.scm /mnt

copies to /mnt all the store items required by the configuration specified in my-os-config.scm. This includes configuration files, packages, and so on. It also creates other essential files needed for the system to operate correctly—e.g., the /etc, /var, and /run directories, and the /bin/sh file.

This command also installs GRUB on the device specified in my-os-config, unless the --no-grub option was passed.

vm

Build a virtual machine that contain the operating system declared in file, and return a script to run that virtual machine (VM).

The VM shares its store with the host system.

vm-image
disk-image

Return a virtual machine or disk image of the operating system declared in file that stands alone. Use the --image-size option to specify the size of the image.

When using vm-image, the returned image is in qcow2 format, which the QEMU emulator can efficiently use.

When using disk-image, a raw disk image is produced; it can be copied as is to a USB stick, for instance. Assuming /dev/sdc is the device corresponding to a USB stick, one can copy the image on it using the following command:

# dd if=$(guix system disk-image my-os.scm) of=/dev/sdc

options can contain any of the common build options provided by guix build (see Invoking guix build). In addition, options can contain one of the following:

--system=system
-s system

Attempt to build for system instead of the host’s system type. This works as per guix build (see Invoking guix build).

--image-size=size

For the vm-image and disk-image actions, create an image of the given size. size may be a number of bytes, or it may include a unit as a suffix, such as MiB for mebibytes and GB for gigabytes.

Note that all the actions above, except build and init, rely on KVM support in the Linux-Libre kernel. Specifically, the machine should have hardware virtualization support, the corresponding KVM kernel module should be loaded, and the /dev/kvm device node must exist and be readable and writable by the user and by the daemon’s build users.


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6.2.8 Defining Services

The (gnu services …) modules define several procedures that allow users to declare the operating system’s services (see Using the Configuration System). These procedures are monadic procedures—i.e., procedures that return a monadic value in the store monad (see The Store Monad). For examples of such procedures, See Services.

The monadic value returned by those procedures is a service definition—a structure as returned by the service form. Service definitions specifies the inputs the service depends on, and an expression to start and stop the service. Behind the scenes, service definitions are “translated” into the form suitable for the configuration file of dmd, the init system (see Services in GNU dmd Manual).

As an example, here is what the nscd-service procedure looks like:

(define (nscd-service)
  (with-monad %store-monad
    (return (service
             (documentation "Run libc's name service cache daemon.")
             (provision '(nscd))
             (activate #~(begin
                           (use-modules (guix build utils))
                           (mkdir-p "/var/run/nscd")))
             (start #~(make-forkexec-constructor
                       (string-append #$glibc "/sbin/nscd")
                       "-f" "/dev/null" "--foreground"))
             (stop #~(make-kill-destructor))
             (respawn? #f)))))

The activate, start, and stop fields are G-expressions (see G-Expressions). The activate field contains a script to run at “activation” time; it makes sure that the /var/run/nscd directory exists before nscd is started.

The start and stop fields refer to dmd’s facilities to start and stop processes (see Service De- and Constructors in GNU dmd Manual). The provision field specifies the name under which this service is known to dmd, and documentation specifies on-line documentation. Thus, the commands deco start ncsd, deco stop nscd, and deco doc nscd will do what you would expect (see Invoking deco in GNU dmd Manual).


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6.3 Installing Debugging Files

Program binaries, as produced by the GCC compilers for instance, are typically written in the ELF format, with a section containing debugging information. Debugging information is what allows the debugger, GDB, to map binary code to source code; it is required to debug a compiled program in good conditions.

The problem with debugging information is that is takes up a fair amount of disk space. For example, debugging information for the GNU C Library weighs in at more than 60 MiB. Thus, as a user, keeping all the debugging info of all the installed programs is usually not an option. Yet, space savings should not come at the cost of an impediment to debugging—especially in the GNU system, which should make it easier for users to exert their computing freedom (see GNU Distribution).

Thankfully, the GNU Binary Utilities (Binutils) and GDB provide a mechanism that allows users to get the best of both worlds: debugging information can be stripped from the binaries and stored in separate files. GDB is then able to load debugging information from those files, when they are available (see Separate Debug Files in Debugging with GDB).

The GNU distribution takes advantage of this by storing debugging information in the lib/debug sub-directory of a separate package output unimaginatively called debug (see Packages with Multiple Outputs). Users can choose to install the debug output of a package when they need it. For instance, the following command installs the debugging information for the GNU C Library and for GNU Guile:

guix package -i glibc:debug guile:debug

GDB must then be told to look for debug files in the user’s profile, by setting the debug-file-directory variable (consider setting it from the ~/.gdbinit file, see Startup in Debugging with GDB):

(gdb) set debug-file-directory ~/.guix-profile/lib/debug

From there on, GDB will pick up debugging information from the .debug files under ~/.guix-profile/lib/debug.

In addition, you will most likely want GDB to be able to show the source code being debugged. To do that, you will have to unpack the source code of the package of interest (obtained with guix build --source, see Invoking guix build), and to point GDB to that source directory using the directory command (see directory in Debugging with GDB).

The debug output mechanism in Guix is implemented by the gnu-build-system (see Build Systems). Currently, it is opt-in—debugging information is available only for those packages whose definition explicitly declares a debug output. This may be changed to opt-out in the future, if our build farm servers can handle the load. To check whether a package has a debug output, use guix package --list-available (see Invoking guix package).


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6.4 Package Modules

From a programming viewpoint, the package definitions of the GNU distribution are provided by Guile modules in the (gnu packages …) name space11 (see Guile modules in GNU Guile Reference Manual). For instance, the (gnu packages emacs) module exports a variable named emacs, which is bound to a <package> object (see Defining Packages).

The (gnu packages …) module name space is special: it is automatically scanned for packages by the command-line tools. For instance, when running guix package -i emacs, all the (gnu packages …) modules are scanned until one that exports a package object whose name is emacs is found. This package search facility is implemented in the (gnu packages) module.

Users can store package definitions in modules with different names—e.g., (my-packages emacs). In that case, commands such as guix package and guix build have to be used with the -e option so that they know where to find the package.

The distribution is fully bootstrapped and self-contained: each package is built based solely on other packages in the distribution. The root of this dependency graph is a small set of bootstrap binaries, provided by the (gnu packages bootstrap) module. For more information on bootstrapping, Bootstrapping.


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6.5 Packaging Guidelines

The GNU distribution is nascent and may well lack some of your favorite packages. This section describes how you can help make the distribution grow. See Contributing, for additional information on how you can help.

Free software packages are usually distributed in the form of source code tarballs—typically tar.gz files that contain all the source files. Adding a package to the distribution means essentially two things: adding a recipe that describes how to build the package, including a list of other packages required to build it, and adding package meta-data along with that recipe, such as a description and licensing information.

In Guix all this information is embodied in package definitions. Package definitions provide a high-level view of the package. They are written using the syntax of the Scheme programming language; in fact, for each package we define a variable bound to the package definition, and export that variable from a module (see Package Modules). However, in-depth Scheme knowledge is not a prerequisite for creating packages. For more information on package definitions, Defining Packages.

Once a package definition is in place, stored in a file in the Guix source tree, it can be tested using the guix build command (see Invoking guix build). For example, assuming the new package is called gnew, you may run this command from the Guix build tree:

./pre-inst-env guix build gnew --keep-failed

Using --keep-failed makes it easier to debug build failures since it provides access to the failed build tree. Another useful command-line option when debugging is --log-file, to access the build log.

If the package is unknown to the guix command, it may be that the source file contains a syntax error, or lacks a define-public clause to export the package variable. To figure it out, you may load the module from Guile to get more information about the actual error:

./pre-inst-env guile -c '(use-modules (gnu packages gnew))'

Once your package builds correctly, please send us a patch (see Contributing). Well, if you need help, we will be happy to help you too. Once the patch is committed in the Guix repository, the new package automatically gets built on the supported platforms by our continuous integration system.

Users can obtain the new package definition simply by running guix pull (see Invoking guix pull). When hydra.gnu.org is done building the package, installing the package automatically downloads binaries from there (see Substitutes). The only place where human intervention is needed is to review and apply the patch.


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6.5.1 Software Freedom

The GNU operating system has been developed so that users can have freedom in their computing. GNU is free software, meaning that users have the four essential freedoms: to run the program, to study and change the program in source code form, to redistribute exact copies, and to distribute modified versions. Packages found in the GNU distribution provide only software that conveys these four freedoms.

In addition, the GNU distribution follow the free software distribution guidelines. Among other things, these guidelines reject non-free firmware, recommendations of non-free software, and discuss ways to deal with trademarks and patents.

Some packages contain a small and optional subset that violates the above guidelines, for instance because this subset is itself non-free code. When that happens, the offending items are removed with appropriate patches or code snippets in the package definition’s origin form (see Defining Packages). That way, guix build --source returns the “freed” source rather than the unmodified upstream source.


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6.5.2 Package Naming

A package has actually two names associated with it: First, there is the name of the Scheme variable, the one following define-public. By this name, the package can be made known in the Scheme code, for instance as input to another package. Second, there is the string in the name field of a package definition. This name is used by package management commands such as guix package and guix build.

Both are usually the same and correspond to the lowercase conversion of the project name chosen upstream, with underscores replaced with hyphens. For instance, GNUnet is available as gnunet, and SDL_net as sdl-net.

We do not add lib prefixes for library packages, unless these are already part of the official project name. But see see Python Modules and Perl Modules for special rules concerning modules for the Python and Perl languages.


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6.5.3 Version Numbers

We usually package only the latest version of a given free software project. But sometimes, for instance for incompatible library versions, two (or more) versions of the same package are needed. These require different Scheme variable names. We use the name as defined in Package Naming for the most recent version; previous versions use the same name, suffixed by - and the smallest prefix of the version number that may distinguish the two versions.

The name inside the package definition is the same for all versions of a package and does not contain any version number.

For instance, the versions 2.24.20 and 3.9.12 of GTK+ may be packaged as follows:

(define-public gtk+
  (package
   (name "gtk+")
   (version "3.9.12")
   ...))
(define-public gtk+-2
  (package
   (name "gtk+")
   (version "2.24.20")
   ...))

If we also wanted GTK+ 3.8.2, this would be packaged as

(define-public gtk+-3.8
  (package
   (name "gtk+")
   (version "3.8.2")
   ...))

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6.5.4 Python Modules

We currently package Python 2 and Python 3, under the Scheme variable names python-2 and python as explained in Version Numbers. To avoid confusion and naming clashes with other programming languages, it seems desirable that the name of a package for a Python module contains the word python.

Some modules are compatible with only one version of Python, others with both. If the package Foo compiles only with Python 3, we name it python-foo; if it compiles only with Python 2, we name it python2-foo. If it is compatible with both versions, we create two packages with the corresponding names.

If a project already contains the word python, we drop this; for instance, the module python-dateutil is packaged under the names python-dateutil and python2-dateutil.


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6.5.5 Perl Modules

Perl programs standing for themselves are named as any other package, using the lowercase upstream name. For Perl packages containing a single class, we use the lowercase class name, replace all occurrences of :: by dashes and prepend the prefix perl-. So the class XML::Parser becomes perl-xml-parser. Modules containing several classes keep their lowercase upstream name and are also prepended by perl-. Such modules tend to have the word perl somewhere in their name, which gets dropped in favor of the prefix. For instance, libwww-perl becomes perl-libwww.


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6.6 Bootstrapping

Bootstrapping in our context refers to how the distribution gets built “from nothing”. Remember that the build environment of a derivation contains nothing but its declared inputs (see Introduction). So there’s an obvious chicken-and-egg problem: how does the first package get built? How does the first compiler get compiled? Note that this is a question of interest only to the curious hacker, not to the regular user, so you can shamelessly skip this section if you consider yourself a “regular user”.

The GNU system is primarily made of C code, with libc at its core. The GNU build system itself assumes the availability of a Bourne shell and command-line tools provided by GNU Coreutils, Awk, Findutils, ‘sed’, and ‘grep’. Furthermore, build programs—programs that run ./configure, make, etc.—are written in Guile Scheme (see Derivations). Consequently, to be able to build anything at all, from scratch, Guix relies on pre-built binaries of Guile, GCC, Binutils, libc, and the other packages mentioned above—the bootstrap binaries.

These bootstrap binaries are “taken for granted”, though we can also re-create them if needed (more on that later).

Preparing to Use the Bootstrap Binaries

Dependency graph of the early bootstrap derivations

The figure above shows the very beginning of the dependency graph of the distribution, corresponding to the package definitions of the (gnu packages bootstrap) module. At this level of detail, things are slightly complex. First, Guile itself consists of an ELF executable, along with many source and compiled Scheme files that are dynamically loaded when it runs. This gets stored in the guile-2.0.7.tar.xz tarball shown in this graph. This tarball is part of Guix’s “source” distribution, and gets inserted into the store with add-to-store (see The Store).

But how do we write a derivation that unpacks this tarball and adds it to the store? To solve this problem, the guile-bootstrap-2.0.drv derivation—the first one that gets built—uses bash as its builder, which runs build-bootstrap-guile.sh, which in turn calls tar to unpack the tarball. Thus, bash, tar, xz, and mkdir are statically-linked binaries, also part of the Guix source distribution, whose sole purpose is to allow the Guile tarball to be unpacked.

Once guile-bootstrap-2.0.drv is built, we have a functioning Guile that can be used to run subsequent build programs. Its first task is to download tarballs containing the other pre-built binaries—this is what the .tar.xz.drv derivations do. Guix modules such as ftp-client.scm are used for this purpose. The module-import.drv derivations import those modules in a directory in the store, using the original layout. The module-import-compiled.drv derivations compile those modules, and write them in an output directory with the right layout. This corresponds to the #:modules argument of build-expression->derivation (see Derivations).

Finally, the various tarballs are unpacked by the derivations gcc-bootstrap-0.drv, glibc-bootstrap-0.drv, etc., at which point we have a working C tool chain.

Building the Build Tools

Bootstrapping is complete when we have a full tool chain that does not depend on the pre-built bootstrap tools discussed above. This no-dependency requirement is verified by checking whether the files of the final tool chain contain references to the /gnu/store directories of the bootstrap inputs. The process that leads to this “final” tool chain is described by the package definitions found in the (gnu packages base) module.

The first tool that gets built with the bootstrap binaries is GNU Make, which is a prerequisite for all the following packages. From there Findutils and Diffutils get built.

Then come the first-stage Binutils and GCC, built as pseudo cross tools—i.e., with --target equal to --host. They are used to build libc. Thanks to this cross-build trick, this libc is guaranteed not to hold any reference to the initial tool chain.

From there the final Binutils and GCC are built. GCC uses ld from the final Binutils, and links programs against the just-built libc. This tool chain is used to build the other packages used by Guix and by the GNU Build System: Guile, Bash, Coreutils, etc.

And voilà! At this point we have the complete set of build tools that the GNU Build System expects. These are in the %final-inputs variables of the (gnu packages base) module, and are implicitly used by any package that uses gnu-build-system (see Defining Packages).

Building the Bootstrap Binaries

Because the final tool chain does not depend on the bootstrap binaries, those rarely need to be updated. Nevertheless, it is useful to have an automated way to produce them, should an update occur, and this is what the (gnu packages make-bootstrap) module provides.

The following command builds the tarballs containing the bootstrap binaries (Guile, Binutils, GCC, libc, and a tarball containing a mixture of Coreutils and other basic command-line tools):

guix build bootstrap-tarballs

The generated tarballs are those that should be referred to in the (gnu packages bootstrap) module mentioned at the beginning of this section.

Still here? Then perhaps by now you’ve started to wonder: when do we reach a fixed point? That is an interesting question! The answer is unknown, but if you would like to investigate further (and have significant computational and storage resources to do so), then let us know.


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6.7 Porting to a New Platform

As discussed above, the GNU distribution is self-contained, and self-containment is achieved by relying on pre-built “bootstrap binaries” (see Bootstrapping). These binaries are specific to an operating system kernel, CPU architecture, and application binary interface (ABI). Thus, to port the distribution to a platform that is not yet supported, one must build those bootstrap binaries, and update the (gnu packages bootstrap) module to use them on that platform.

Fortunately, Guix can cross compile those bootstrap binaries. When everything goes well, and assuming the GNU tool chain supports the target platform, this can be as simple as running a command like this one:

guix build --target=armv5tel-linux-gnueabi bootstrap-tarballs

Once these are built, the (gnu packages bootstrap) module needs to be updated to refer to these binaries on the target platform. In addition, the glibc-dynamic-linker procedure in that module must be augmented to return the right file name for libc’s dynamic linker on that platform; likewise, system->linux-architecture in (gnu packages linux) must be taught about the new platform.

In practice, there may be some complications. First, it may be that the extended GNU triplet that specifies an ABI (like the eabi suffix above) is not recognized by all the GNU tools. Typically, glibc recognizes some of these, whereas GCC uses an extra --with-abi configure flag (see gcc.scm for examples of how to handle this). Second, some of the required packages could fail to build for that platform. Lastly, the generated binaries could be broken for some reason.


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7 Contributing

This project is a cooperative effort, and we need your help to make it grow! Please get in touch with us on guix-devel@gnu.org and #guix on the Freenode IRC network. We welcome ideas, bug reports, patches, and anything that may be helpful to the project. We particularly welcome help on packaging (see Packaging Guidelines).

Please see the HACKING file that comes with the Guix source code for practical details about contributions.


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8 Acknowledgments

Guix is based on the Nix package manager, which was designed and implemented by Eelco Dolstra. Nix pioneered functional package management, and promoted unprecedented features, such as transactional package upgrades and rollbacks, per-user profiles, and referentially transparent build processes. Without this work, Guix would not exist.

The Nix-based software distributions, Nixpkgs and NixOS, have also been an inspiration for Guix.


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Appendix A GNU Free Documentation License

Version 1.3, 3 November 2008
Copyright © 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc.
http://fsf.org/

Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.
  1. PREAMBLE

    The purpose of this License is to make a manual, textbook, or other functional and useful document free in the sense of freedom: to assure everyone the effective freedom to copy and redistribute it, with or without modifying it, either commercially or noncommercially. Secondarily, this License preserves for the author and publisher a way to get credit for their work, while not being considered responsible for modifications made by others.

    This License is a kind of “copyleft”, which means that derivative works of the document must themselves be free in the same sense. It complements the GNU General Public License, which is a copyleft license designed for free software.

    We have designed this License in order to use it for manuals for free software, because free software needs free documentation: a free program should come with manuals providing the same freedoms that the software does. But this License is not limited to software manuals; it can be used for any textual work, regardless of subject matter or whether it is published as a printed book. We recommend this License principally for works whose purpose is instruction or reference.

  2. APPLICABILITY AND DEFINITIONS

    This License applies to any manual or other work, in any medium, that contains a notice placed by the copyright holder saying it can be distributed under the terms of this License. Such a notice grants a world-wide, royalty-free license, unlimited in duration, to use that work under the conditions stated herein. The “Document”, below, refers to any such manual or work. Any member of the public is a licensee, and is addressed as “you”. You accept the license if you copy, modify or distribute the work in a way requiring permission under copyright law.

    A “Modified Version” of the Document means any work containing the Document or a portion of it, either copied verbatim, or with modifications and/or translated into another language.

    A “Secondary Section” is a named appendix or a front-matter section of the Document that deals exclusively with the relationship of the publishers or authors of the Document to the Document’s overall subject (or to related matters) and contains nothing that could fall directly within that overall subject. (Thus, if the Document is in part a textbook of mathematics, a Secondary Section may not explain any mathematics.) The relationship could be a matter of historical connection with the subject or with related matters, or of legal, commercial, philosophical, ethical or political position regarding them.

    The “Invariant Sections” are certain Secondary Sections whose titles are designated, as being those of Invariant Sections, in the notice that says that the Document is released under this License. If a section does not fit the above definition of Secondary then it is not allowed to be designated as Invariant. The Document may contain zero Invariant Sections. If the Document does not identify any Invariant Sections then there are none.

    The “Cover Texts” are certain short passages of text that are listed, as Front-Cover Texts or Back-Cover Texts, in the notice that says that the Document is released under this License. A Front-Cover Text may be at most 5 words, and a Back-Cover Text may be at most 25 words.

    A “Transparent” copy of the Document means a machine-readable copy, represented in a format whose specification is available to the general public, that is suitable for revising the document straightforwardly with generic text editors or (for images composed of pixels) generic paint programs or (for drawings) some widely available drawing editor, and that is suitable for input to text formatters or for automatic translation to a variety of formats suitable for input to text formatters. A copy made in an otherwise Transparent file format whose markup, or absence of markup, has been arranged to thwart or discourage subsequent modification by readers is not Transparent. An image format is not Transparent if used for any substantial amount of text. A copy that is not “Transparent” is called “Opaque”.

    Examples of suitable formats for Transparent copies include plain ASCII without markup, Texinfo input format, LaTeX input format, SGML or XML using a publicly available DTD, and standard-conforming simple HTML, PostScript or PDF designed for human modification. Examples of transparent image formats include PNG, XCF and JPG. Opaque formats include proprietary formats that can be read and edited only by proprietary word processors, SGML or XML for which the DTD and/or processing tools are not generally available, and the machine-generated HTML, PostScript or PDF produced by some word processors for output purposes only.

    The “Title Page” means, for a printed book, the title page itself, plus such following pages as are needed to hold, legibly, the material this License requires to appear in the title page. For works in formats which do not have any title page as such, “Title Page” means the text near the most prominent appearance of the work’s title, preceding the beginning of the body of the text.

    The “publisher” means any person or entity that distributes copies of the Document to the public.

    A section “Entitled XYZ” means a named subunit of the Document whose title either is precisely XYZ or contains XYZ in parentheses following text that translates XYZ in another language. (Here XYZ stands for a specific section name mentioned below, such as “Acknowledgements”, “Dedications”, “Endorsements”, or “History”.) To “Preserve the Title” of such a section when you modify the Document means that it remains a section “Entitled XYZ” according to this definition.

    The Document may include Warranty Disclaimers next to the notice which states that this License applies to the Document. These Warranty Disclaimers are considered to be included by reference in this License, but only as regards disclaiming warranties: any other implication that these Warranty Disclaimers may have is void and has no effect on the meaning of this License.

  3. VERBATIM COPYING

    You may copy and distribute the Document in any medium, either commercially or noncommercially, provided that this License, the copyright notices, and the license notice saying this License applies to the Document are reproduced in all copies, and that you add no other conditions whatsoever to those of this License. You may not use technical measures to obstruct or control the reading or further copying of the copies you make or distribute. However, you may accept compensation in exchange for copies. If you distribute a large enough number of copies you must also follow the conditions in section 3.

    You may also lend copies, under the same conditions stated above, and you may publicly display copies.

  4. COPYING IN QUANTITY

    If you publish printed copies (or copies in media that commonly have printed covers) of the Document, numbering more than 100, and the Document’s license notice requires Cover Texts, you must enclose the copies in covers that carry, clearly and legibly, all these Cover Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on the back cover. Both covers must also clearly and legibly identify you as the publisher of these copies. The front cover must present the full title with all words of the title equally prominent and visible. You may add other material on the covers in addition. Copying with changes limited to the covers, as long as they preserve the title of the Document and satisfy these conditions, can be treated as verbatim copying in other respects.

    If the required texts for either cover are too voluminous to fit legibly, you should put the first ones listed (as many as fit reasonably) on the actual cover, and continue the rest onto adjacent pages.

    If you publish or distribute Opaque copies of the Document numbering more than 100, you must either include a machine-readable Transparent copy along with each Opaque copy, or state in or with each Opaque copy a computer-network location from which the general network-using public has access to download using public-standard network protocols a complete Transparent copy of the Document, free of added material. If you use the latter option, you must take reasonably prudent steps, when you begin distribution of Opaque copies in quantity, to ensure that this Transparent copy will remain thus accessible at the stated location until at least one year after the last time you distribute an Opaque copy (directly or through your agents or retailers) of that edition to the public.

    It is requested, but not required, that you contact the authors of the Document well before redistributing any large number of copies, to give them a chance to provide you with an updated version of the Document.

  5. MODIFICATIONS

    You may copy and distribute a Modified Version of the Document under the conditions of sections 2 and 3 above, provided that you release the Modified Version under precisely this License, with the Modified Version filling the role of the Document, thus licensing distribution and modification of the Modified Version to whoever possesses a copy of it. In addition, you must do these things in the Modified Version:

    1. Use in the Title Page (and on the covers, if any) a title distinct from that of the Document, and from those of previous versions (which should, if there were any, be listed in the History section of the Document). You may use the same title as a previous version if the original publisher of that version gives permission.
    2. List on the Title Page, as authors, one or more persons or entities responsible for authorship of the modifications in the Modified Version, together with at least five of the principal authors of the Document (all of its principal authors, if it has fewer than five), unless they release you from this requirement.
    3. State on the Title page the name of the publisher of the Modified Version, as the publisher.
    4. Preserve all the copyright notices of the Document.
    5. Add an appropriate copyright notice for your modifications adjacent to the other copyright notices.
    6. Include, immediately after the copyright notices, a license notice giving the public permission to use the Modified Version under the terms of this License, in the form shown in the Addendum below.
    7. Preserve in that license notice the full lists of Invariant Sections and required Cover Texts given in the Document’s license notice.
    8. Include an unaltered copy of this License.
    9. Preserve the section Entitled “History”, Preserve its Title, and add to it an item stating at least the title, year, new authors, and publisher of the Modified Version as given on the Title Page. If there is no section Entitled “History” in the Document, create one stating the title, year, authors, and publisher of the Document as given on its Title Page, then add an item describing the Modified Version as stated in the previous sentence.
    10. Preserve the network location, if any, given in the Document for public access to a Transparent copy of the Document, and likewise the network locations given in the Document for previous versions it was based on. These may be placed in the “History” section. You may omit a network location for a work that was published at least four years before the Document itself, or if the original publisher of the version it refers to gives permission.
    11. For any section Entitled “Acknowledgements” or “Dedications”, Preserve the Title of the section, and preserve in the section all the substance and tone of each of the contributor acknowledgements and/or dedications given therein.
    12. Preserve all the Invariant Sections of the Document, unaltered in their text and in their titles. Section numbers or the equivalent are not considered part of the section titles.
    13. Delete any section Entitled “Endorsements”. Such a section may not be included in the Modified Version.
    14. Do not retitle any existing section to be Entitled “Endorsements” or to conflict in title with any Invariant Section.
    15. Preserve any Warranty Disclaimers.

    If the Modified Version includes new front-matter sections or appendices that qualify as Secondary Sections and contain no material copied from the Document, you may at your option designate some or all of these sections as invariant. To do this, add their titles to the list of Invariant Sections in the Modified Version’s license notice. These titles must be distinct from any other section titles.

    You may add a section Entitled “Endorsements”, provided it contains nothing but endorsements of your Modified Version by various parties—for example, statements of peer review or that the text has been approved by an organization as the authoritative definition of a standard.

    You may add a passage of up to five words as a Front-Cover Text, and a passage of up to 25 words as a Back-Cover Text, to the end of the list of Cover Texts in the Modified Version. Only one passage of Front-Cover Text and one of Back-Cover Text may be added by (or through arrangements made by) any one entity. If the Document already includes a cover text for the same cover, previously added by you or by arrangement made by the same entity you are acting on behalf of, you may not add another; but you may replace the old one, on explicit permission from the previous publisher that added the old one.

    The author(s) and publisher(s) of the Document do not by this License give permission to use their names for publicity for or to assert or imply endorsement of any Modified Version.

  6. COMBINING DOCUMENTS

    You may combine the Document with other documents released under this License, under the terms defined in section 4 above for modified versions, provided that you include in the combination all of the Invariant Sections of all of the original documents, unmodified, and list them all as Invariant Sections of your combined work in its license notice, and that you preserve all their Warranty Disclaimers.

    The combined work need only contain one copy of this License, and multiple identical Invariant Sections may be replaced with a single copy. If there are multiple Invariant Sections with the same name but different contents, make the title of each such section unique by adding at the end of it, in parentheses, the name of the original author or publisher of that section if known, or else a unique number. Make the same adjustment to the section titles in the list of Invariant Sections in the license notice of the combined work.

    In the combination, you must combine any sections Entitled “History” in the various original documents, forming one section Entitled “History”; likewise combine any sections Entitled “Acknowledgements”, and any sections Entitled “Dedications”. You must delete all sections Entitled “Endorsements.”

  7. COLLECTIONS OF DOCUMENTS

    You may make a collection consisting of the Document and other documents released under this License, and replace the individual copies of this License in the various documents with a single copy that is included in the collection, provided that you follow the rules of this License for verbatim copying of each of the documents in all other respects.

    You may extract a single document from such a collection, and distribute it individually under this License, provided you insert a copy of this License into the extracted document, and follow this License in all other respects regarding verbatim copying of that document.

  8. AGGREGATION WITH INDEPENDENT WORKS

    A compilation of the Document or its derivatives with other separate and independent documents or works, in or on a volume of a storage or distribution medium, is called an “aggregate” if the copyright resulting from the compilation is not used to limit the legal rights of the compilation’s users beyond what the individual works permit. When the Document is included in an aggregate, this License does not apply to the other works in the aggregate which are not themselves derivative works of the Document.

    If the Cover Text requirement of section 3 is applicable to these copies of the Document, then if the Document is less than one half of the entire aggregate, the Document’s Cover Texts may be placed on covers that bracket the Document within the aggregate, or the electronic equivalent of covers if the Document is in electronic form. Otherwise they must appear on printed covers that bracket the whole aggregate.

  9. TRANSLATION

    Translation is considered a kind of modification, so you may distribute translations of the Document under the terms of section 4. Replacing Invariant Sections with translations requires special permission from their copyright holders, but you may include translations of some or all Invariant Sections in addition to the original versions of these Invariant Sections. You may include a translation of this License, and all the license notices in the Document, and any Warranty Disclaimers, provided that you also include the original English version of this License and the original versions of those notices and disclaimers. In case of a disagreement between the translation and the original version of this License or a notice or disclaimer, the original version will prevail.

    If a section in the Document is Entitled “Acknowledgements”, “Dedications”, or “History”, the requirement (section 4) to Preserve its Title (section 1) will typically require changing the actual title.

  10. TERMINATION

    You may not copy, modify, sublicense, or distribute the Document except as expressly provided under this License. Any attempt otherwise to copy, modify, sublicense, or distribute it is void, and will automatically terminate your rights under this License.

    However, if you cease all violation of this License, then your license from a particular copyright holder is reinstated (a) provisionally, unless and until the copyright holder explicitly and finally terminates your license, and (b) permanently, if the copyright holder fails to notify you of the violation by some reasonable means prior to 60 days after the cessation.

    Moreover, your license from a particular copyright holder is reinstated permanently if the copyright holder notifies you of the violation by some reasonable means, this is the first time you have received notice of violation of this License (for any work) from that copyright holder, and you cure the violation prior to 30 days after your receipt of the notice.

    Termination of your rights under this section does not terminate the licenses of parties who have received copies or rights from you under this License. If your rights have been terminated and not permanently reinstated, receipt of a copy of some or all of the same material does not give you any rights to use it.

  11. FUTURE REVISIONS OF THIS LICENSE

    The Free Software Foundation may publish new, revised versions of the GNU Free Documentation License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns. See http://www.gnu.org/copyleft/.

    Each version of the License is given a distinguishing version number. If the Document specifies that a particular numbered version of this License “or any later version” applies to it, you have the option of following the terms and conditions either of that specified version or of any later version that has been published (not as a draft) by the Free Software Foundation. If the Document does not specify a version number of this License, you may choose any version ever published (not as a draft) by the Free Software Foundation. If the Document specifies that a proxy can decide which future versions of this License can be used, that proxy’s public statement of acceptance of a version permanently authorizes you to choose that version for the Document.

  12. RELICENSING

    “Massive Multiauthor Collaboration Site” (or “MMC Site”) means any World Wide Web server that publishes copyrightable works and also provides prominent facilities for anybody to edit those works. A public wiki that anybody can edit is an example of such a server. A “Massive Multiauthor Collaboration” (or “MMC”) contained in the site means any set of copyrightable works thus published on the MMC site.

    “CC-BY-SA” means the Creative Commons Attribution-Share Alike 3.0 license published by Creative Commons Corporation, a not-for-profit corporation with a principal place of business in San Francisco, California, as well as future copyleft versions of that license published by that same organization.

    “Incorporate” means to publish or republish a Document, in whole or in part, as part of another Document.

    An MMC is “eligible for relicensing” if it is licensed under this License, and if all works that were first published under this License somewhere other than this MMC, and subsequently incorporated in whole or in part into the MMC, (1) had no cover texts or invariant sections, and (2) were thus incorporated prior to November 1, 2008.

    The operator of an MMC Site may republish an MMC contained in the site under CC-BY-SA on the same site at any time before August 1, 2009, provided the MMC is eligible for relicensing.

ADDENDUM: How to use this License for your documents

To use this License in a document you have written, include a copy of the License in the document and put the following copyright and license notices just after the title page:

  Copyright (C)  year  your name.
  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''.

If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts, replace the “with…Texts.” line with this:

    with the Invariant Sections being list their titles, with
    the Front-Cover Texts being list, and with the Back-Cover Texts
    being list.

If you have Invariant Sections without Cover Texts, or some other combination of the three, merge those two alternatives to suit the situation.

If your document contains nontrivial examples of program code, we recommend releasing these examples in parallel under your choice of free software license, such as the GNU General Public License, to permit their use in free software.


Next: , Previous: , Up: Top   [Contents][Index]

Concept Index

Jump to:   A   B   C   D   F   G   I   M   O   P   R   S   V  
Index Entry  Section

A
authorizing, archives: Invoking guix archive

B
bootstrap binaries: Bootstrapping
bootstrapping: Bootstrapping
build code quoting: G-Expressions
build environment: Invoking guix-daemon
build hook: Daemon Offload Setup
build hook: Invoking guix-daemon
build phases: Build Systems
build system: Build Systems
build users: Build Environment Setup

C
chroot: Build Environment Setup
chroot: Invoking guix-daemon
common build options: Invoking guix build
container, build environment: Invoking guix-daemon
cross-compilation: Defining Packages
cross-compilation: Invoking guix build

D
daemon: Setting Up the Daemon
debugging files: Installing Debugging Files
derivation: Programming Interface
derivation path: Derivations
derivations: Derivations
digital signatures: Substitutes

F
functional package management: Introduction

G
G-expression: G-Expressions
garbage collector: Invoking guix gc
GNU Build System: Defining Packages

I
initial RAM disk (initrd): Initial RAM Disk
initrd (initial RAM disk): Initial RAM Disk

M
monad: The Store Monad
monadic functions: The Store Monad
monadic values: The Store Monad
multiple-output packages: Packages with Multiple Outputs

O
offloading: Daemon Offload Setup

P
package outputs: Packages with Multiple Outputs
patches: Defining Packages
pre-built binaries: Substitutes
propagated inputs: Invoking guix package

R
reproducibility: Features
reproducible builds: Invoking guix-daemon
reproducible builds: Features

S
search paths: Invoking guix package
security: Substitutes
service definition: Defining Services
setuid programs: Setuid Programs
signing, archives: Invoking guix archive
store: Introduction
store: The Store
store paths: The Store
strata of code: G-Expressions
substituter: Packaging Guidelines
substitutes: Invoking guix-daemon
substitutes: Features
substitutes: Substitutes
system configuration: System Configuration
system services: Services

V
virtual machine: Invoking guix system

Jump to:   A   B   C   D   F   G   I   M   O   P   R   S   V  

Previous: , Up: Top   [Contents][Index]

Programming Index

Jump to:   #   %   (   >  
A   B   C   D   E   F   G   H   I   L   M   N   O   P   R   S   T   U   V   W  
Index Entry  Section

#
#~: G-Expressions

%
%base-file-systems: File Systems
%base-groups: User Accounts
%base-packages: Using the Configuration System
%base-services: Using the Configuration System
%base-services: Base Services
%binary-format-file-system: File Systems
%devtmpfs-file-system: File Systems
%fuse-control-file-system: File Systems
%pseudo-terminal-file-system: File Systems
%setuid-programs: Setuid Programs
%shared-memory-file-system: File Systems
%standard-phases: Build Systems
%store-monad: The Store Monad

(
(gexp: G-Expressions

>
>>=: The Store Monad

A
add-text-to-store: The Store

B
base-initrd: Initial RAM Disk
build-derivations: The Store
build-expression->derivation: Derivations

C
close-connection: The Store
cmake-build-system: Build Systems
current-build-output-port: The Store

D
derivation: Derivations

E
expression->initrd: Initial RAM Disk

F
file-system: File Systems

G
gexp->derivation: G-Expressions
gexp->file: G-Expressions
gexp->script: G-Expressions
gexp?: G-Expressions
gnu-build-system: Build Systems
guix-service: Base Services

H
host-name-service: Base Services

I
interned-file: The Store Monad

L
lsh-service: Networking Services

M
mingetty-service: Base Services
mlet: The Store Monad
mlet*: The Store Monad

N
nscd-service: Base Services

O
open-connection: The Store
operating-system: Using the Configuration System
operating-system-derivation: Using the Configuration System

P
package->derivation: The Store Monad
package-cross-derivation: Defining Packages
package-derivation: Defining Packages
package-file: The Store Monad
perl-build-system: Build Systems
python-build-system: Build Systems

R
return: The Store Monad
run-with-store: The Store Monad

S
slim-service: X Window
static-networking-service: Networking Services
syslog-service: Base Services

T
text-file: The Store Monad
text-file*: The Store Monad
tor-service: Networking Services
trivial-build-system: Build Systems

U
udev-service: Base Services
user-account: User Accounts
user-group: User Accounts

V
valid-path?: The Store

W
with-monad: The Store Monad

Jump to:   #   %   (   >  
A   B   C   D   E   F   G   H   I   L   M   N   O   P   R   S   T   U   V   W  

Footnotes

(1)

“Guix” is pronounced like “geeks”, or “ɡiːks” using the international phonetic alphabet (IPA).

(2)

“Mostly”, because while the set of files that appear in the chroot’s /dev is fixed, most of these files can only be created if the host has them.

(3)

Simple package definitions like the one above may be automatically converted from the Nixpkgs distribution using the guix import command.

(4)

Please see the (guix build gnu-build-system) modules for more details about the build phases.

(5)

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.

(6)

The term 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 essays and code on this topic, refers to this kind of code generation as staging.

(7)

Currently, this only works for GNU packages.

(8)

The term “free” here refers to the freedom provided to users of that software.

(9)

Technically, this is a list of monadic services. See The Store Monad.

(10)

This action is usable only on systems already running GNU.

(11)

Note that packages under the (gnu packages …) module name space are not necessarily “GNU packages”. This module naming scheme follows the usual Guile module naming convention: gnu means that these modules are distributed as part of the GNU system, and packages identifies modules that define packages.