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.