GNU Guix Reference Manual

Table of Contents

GNU Guix

This document describes GNU Guix version 0.2, a functional package management tool written for the GNU system.

Copyright © 2012, 2013 Ludovic Courtès

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.”

1 Introduction

GNU Guix¹ is a functional package management tool for the GNU system. Package management consists in all the activities that relate to building packages from source, honoring the build-time and run-time dependencies on packages, 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 depended on, and returns the 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. Last but not least, a build function 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 dedicated “chroots”, 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 /nix/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 upgrades and rollback, per-user installation, and garbage collection of packages (see Features).

Guix has a command-line interface allowing users to build, install, upgrade, and remove packages, as well as a Scheme programming interface. The remainder of this manual describes them.

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.

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.

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.

2.1 Requirements

GNU Guix depends on the following packages:

• GNU Guile 2.0.x;
• GNU libgcrypt

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

• SQLite 3
• libbz2
• GCC’s g++

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 store meta-data about the store is located, among other things.) The default values are --with-store-dir=/nix/store and --localstatedir=/nix/var. Note that --disable-daemon is orthogonal and is not required if your goal is to share the same store as Nix.

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 Guix 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.

In a standard multi-user setup, Guix and its daemon—the guix-daemon program—are installed by the system administrator; /nix/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 $i" guix-builder$i;
  done

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

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

Guix may also be used in a single-user setup, with guix-daemon running as an unprivileged user. However, to maximize non-interference of build processes, the daemon still needs to perform certain operations that are restricted to root on GNU/Linux: it should be able to run build processes in a chroot, and to run them under different UIDs. To that end, the nix-setuid-helper program is provided; it is a small C program (less than 300 lines) that, if it is made setuid root, can be executed by the daemon to perform these operations on its behalf. The root-owned /etc/nix-setuid.conf file is read by nix-setuid-helper; it should contain exactly two words: the user name under which the authorized guix-daemon runs, and the name of the build users group.

If you are installing Guix as an unprivileged user and do not have the ability to make nix-setuid-helper setuid-root, 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.

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.

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.

--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.

--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.

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.

3.1 Features

When using Guix, each package ends up in the package store, in its own directory—something that resembles /nix/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 /nix/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 /nix/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.

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 /nix/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, and helps maximize reproducibility.

This foundation allows Guix to support transparent binary/source deployment. When a pre-built binary for a /nix/store path is available from an external source, Guix just downloads it; otherwise, it builds the package from source, locally.

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 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, guix package emits an error about it.

The options can be among the following:

--install=package

-i package

Install package.

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.

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 sometime 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 package.

--upgrade[=regexp]

-u [regexp]

Upgrade all the installed packages. When regexp is specified, upgrade only installed packages whose name matches 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 empty profile, also known as profile zero—i.e., it 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.

--dry-run

-n

Show what would be done without actually doing it.

--no-substitutes

Build instead of resorting to pre-built substitutes.

--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

--list-installed[=regexp]

-I [regexp]

List currently installed packages in the specified profile. 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 (out for the main files, lib for libraries and possibly headers, etc.), and the source location of its definition.

3.3 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 /nix/store directory.

The garbage collector has a set of known roots: any file under /nix/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).

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 /nix/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.

3.4 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.

--bootstrap

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

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 /nix/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.

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

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:

(use-modules (guix packages)
             (guix download)
             (guix build-system gnu)
             (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)
    (inputs `(("gawk" ,gawk)))
    (synopsis "GNU Hello")
    (description "Yeah...")
    (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".

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

• The source field of the package is an <origin> object. Here, the url-fetch method from (guix download) is used, meaning that the source is a file to be downloaded over FTP or HTTP.

  The mirror://gnu prefix instructs url-fetch to use one of the GNU mirrors defined in (guix download).

  The sha256 field specifies the expected SHA256 hash of the file being downloaded. It is mandatory, and allows Guix to check the integrity of the file. The (base32 …) form introduces the base32 representation of the hash. You can obtain this information with guix download (see Invoking guix download) and guix hash (see Invoking guix hash).

• The build-system field is set to gnu-build-system. The gnu-build-system variable is defined in the (guix build-system gnu) module, and is bound to a <build-system> object.

  Naturally, gnu-build-system represents the familiar GNU Build System, and variants thereof (see configuration and makefile conventions in GNU Coding Standards). In a nutshell, packages using the GNU Build System may be configured, built, and installed with the usual ./configure && make && make check && make install command sequence. This is what gnu-build-system does.

  In addition, gnu-build-system ensures that the “standard” environment for GNU packages is available. This includes tools such as GCC, Coreutils, Bash, Make, Diffutils, and Patch.

• The inputs field specifies inputs to the build process—i.e., build-time or run-time dependencies of the package. Here, we define an input called "gawk" whose value is that of the gawk variable; gawk is itself bound to a <package> object.

  Note that GCC, Coreutils, Bash, and other essential tools do not need to be specified as inputs here. Instead, gnu-build-system takes care of ensuring that they are present.

  However, any other dependencies need to be specified in the inputs field. Any dependency not specified here will simply be unavailable to the build process, possibly leading to a build failure.

There are other fields that package definitions may provide. Of particular interest is the arguments field. When specified, it must be bound to a list of additional arguments to be passed to the build system. For instance, the above definition could be augmented with the following field initializer:

    (arguments `(#:tests? #f
                 #:configure-flags '("--enable-silent-rules")))

These are keyword arguments (see keyword arguments in Guile in GNU Guile Reference Manual). They are passed to gnu-build-system, which interprets them as meaning “do not run make check”, and “run configure with the --enable-silent-rules flag”. The value of these keyword parameters is actually evaluated in the build stratum—i.e., by a Guile process launched by the daemon (see Derivations).

Once a package definition is in place², the package may actually be built using the guix build command-line tool (see Invoking guix build). 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 /nix/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 path and corresponding <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).

4.2 The Store

Conceptually, the store is where derivations that have been successfully built are stored—by default, under /nix/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 paths), and return when the worker is done building them. Return #t on success.

This section is currently incomplete.

4.3 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:

• The outputs of the derivation—derivations produce at least one file or directory in the store, but may produce more.
• The inputs of the derivations, which may be other derivations or plain files in the store (patches, build scripts, etc.)
• The system type targeted by the derivation—e.g., x86_64-linux.
• The file name of a build script in the store, along with the arguments to be passed.
• A list of environment variables to be defined.

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 system builder args env-vars inputs [#:outputs '("out")] [#:hash #f] [#:hash-algo #f] [#:hash-mode #f]

Build a derivation with the given arguments. Return the resulting store path and <derivation> object.

When hash, hash-algo, and hash-mode are given, a fixed-output derivation is created—i.e., one whose result is known in advance, such as a file download.

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))

(call-with-values
  (lambda ()
    (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" (%current-system)
                  bash `("-e" ,builder)
                  '(("HOME" . "/homeless")) '())))
  list)
⇒ ("/nix/store/…-foo.drv" #<<derivation> …>)

As can be guessed, this primitive is cumbersome to use directly. An improved variant is build-expression->derivation, which allows the caller to directly pass a Guile expression as the build script:

Scheme Procedure: build-expression->derivation store name system exp inputs [#:outputs '("out")] [#:hash #f] [#:hash-algo #f] [#:env-vars '()] [#:modules '()] [#: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.

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 /nix/store/…-goo
                  (call-with-output-file (string-append out "/test")
                    (lambda (p)
                      (display '(hello guix) p))))))
  (build-expression->derivation store "goo" (%current-system)
                                builder '()))

⇒ "/nix/store/…-goo.drv"
⇒ #<<derivation> …>

Remember that the build expression passed to build-expression->derivation is run by a separate Guile process than the one that calls build-expression->derivation: it is run by a Guile process launched by the daemon, typically in a chroot. So, while there is a single language for both the host and the build side, there are really two strata of code: the host-side, and the build-side code³. This distinction is important to keep in mind, notably when using higher-level constructs such as gnu-build-system (see Defining Packages). For this reason, Guix modules that are meant to be used in the build stratum are kept in the (guix build …) name space.

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.

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 /nix/store/…-coreutils-8.19.drv. 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 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.

--source

-S

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

For instance, guix build -S gcc returns something like /nix/store/…-gcc-4.7.2.tar.bz2, which is GCC’s source tarball.

--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.

--derivations

-d

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

--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.

--no-substitutes

Build instead of resorting to pre-built substitutes.

--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.

--root=file

-r file

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

--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.

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.

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.

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.

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 therein⁴.

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.

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.

6 GNU Distribution

Guix comes with a distribution of free software⁵ that form 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 seen by running guix package (see Invoking guix package):

guix package --list-available

The package definitions of the distribution may are provided by Guile modules in the (gnu packages ...) name space—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 provides facilities for searching for packages.

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. These are statically-linked binaries of the core tools without which building anything at all would be impossible.

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.

Building this distribution is a cooperative effort, and you are invited to join! Please get in touch with us on bug-guix@gnu.org. We welcome ideas, bug reports, patches, and anything that may be helpful to the project.

7 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.

Appendix A GNU Free Documentation License

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.

Concept Index

Function Index