The Nix Packages collection (Nixpkgs) is a set of thousands of packages for the Nix package manager, released under a permissive MIT/X11 license. Packages are available for several platforms, and can be used with the Nix package manager on most GNU/Linux distributions as well as NixOS.

This manual primarily describes how to write packages for the Nix Packages collection (Nixpkgs). Thus it’s mainly for packagers and developers who want to add packages to Nixpkgs. If you like to learn more about the Nix package manager and the Nix expression language, then you are kindly referred to the Nix manual. The NixOS distribution is documented in the NixOS manual.

Overview of Nixpkgs

Nix expressions describe how to build packages from source and are collected in the nixpkgs repository. Also included in the collection are Nix expressions for NixOS modules. With these expressions the Nix package manager can build binary packages.

Packages, including the Nix packages collection, are distributed through channels. The collection is distributed for users of Nix on non-NixOS distributions through the channel nixpkgs. Users of NixOS generally use one of the nixos-* channels, e.g. nixos-19.09, which includes all packages and modules for the stable NixOS 19.09. Stable NixOS releases are generally only given security updates. More up to date packages and modules are available via the nixos-unstable channel.

Both nixos-unstable and nixpkgs follow the master branch of the Nixpkgs repository, although both do lag the master branch by generally a couple of days. Updates to a channel are distributed as soon as all tests for that channel pass, e.g. this table shows the status of tests for the nixpkgs channel.

The tests are conducted by a cluster called Hydra, which also builds binary packages from the Nix expressions in Nixpkgs for x86_64-linux, i686-linux and x86_64-darwin. The binaries are made available via a binary cache.

The current Nix expressions of the channels are available in the nixpkgs repository in branches that correspond to the channel names (e.g. nixos-19.09-small).