Channel branches: Difference between revisions

Nixpkgs is the Git repository containing all package recipes and NixOS module declarations. Installing packages directly from the <code>master</code> branch of the Nixpkgs repository is possible but risky, since Git commits are merged into <code>master</code> before being heavily tested. That is where channel branches are useful.

A "channel branch" is Git branch with the "verified" Git commits in Nixpkgs that is exposed at [https://channels.nixos.org channels.nixos.org]. There is also a [https://status.nixos.org channel status webpage] that tracks the age of channel branches.

Each channel branch follows a corresponding development branch to which new commits are first added. These new commits are then "verified" using the [[Hydra]] continuous integration system, where each channel branch corresponds to building any new or updated packages for that branch and perform the associated tests. A channel branch is updated once its builds succeeds for a new commit. Contrary to users of the development branches, channel branch users will benefit from both "verified" commits and pre-built packages from the [https://cache.nixos.org public binary cache].

** Stable channels (<code>nixos-23.11</code>) only provide conservative updates for fixing bugs and security vulnerabilities, but do not receive major updates after the initial release. New stable channels are released every six months.

** Unstable channels (<code>nixos-unstable</code>, <code>nixpkgs-unstable</code>) follow the <code>master</code> branch of Nixpkgs, delivering the latest tested updates on a rolling basis.

** Large channels (<code>nixos-23.11</code>, <code>nixos-unstable</code>) are updated only after Hydra has finished building the full breadth of Nixpkgs.

** Small channels (<code>nixos-23.11-small</code>, <code>nixos-unstable-small</code>) are identical to large channels, but are updated as soon as Hydra has finished building a defined set of commonly-used packages. Thus, users following these channels will get faster updates but may need to build any packages they use from outside the defined set themselves. These channels are intended to be used for server setups, for example.

NixOS uses [https://nixos.org/manual/nix/stable/command-ref/files/profiles Nix profiles] for the <code>root</code> user to refer different versions of the system-wide configuration. Profiles set for other users only control the user environment for that user.