8.1 Package Modules

From a programming viewpoint, the package definitions of the GNU distribution are provided by Guile modules in the (gnu packages …) name space¹⁷ (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 automatically scanned for packages by the command-line tools. For instance, when running guix install 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)¹⁸. There are two ways to make these package definitions visible to the user interfaces:

1. By adding the directory containing your package modules to the search path with the -L flag of guix package and other commands (see Common Build Options), or by setting the GUIX_PACKAGE_PATH environment variable described below.
2. By defining a channel and configuring guix pull so that it pulls from it. A channel is essentially a Git repository containing package modules. See Channels, for more information on how to define and use channels.

GUIX_PACKAGE_PATH works similarly to other search path variables:

Environment Variable: GUIX_PACKAGE_PATH

This is a colon-separated list of directories to search for additional package modules. Directories listed in this variable take precedence over the own modules of the distribution.

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, see Bootstrapping.