Channel branches
Nix Channels are mechanisms for distributing Nix expressions as well as the associated binaries for them; a Nix channel corresponds to a repository in a conventional package management system. Official Nix channels are automatically updated once tests are passed in Nixpkgs' Hydra instance. It is also possible to create one's own Nix channels, but here we focus the official channels.
The official channels
Packages for Nix, as well as modules for NixOS are distributed through a number of channels. These channels can be broadly categorized into stable and unstable channels, and large and small channels:
- Stable/unstable:
- Stable channels (
nixos-17.09) provide conservative updates for fixing bugs and security vulnerabilities, but do not receive major updates after initial release. New stable channels are released every six months. - Unstable channels (
nixos-unstable,nixos-unstable-small) correspond to the main development branch of Nixpkgs, delivering the latest tested updates on a rolling basis.
- Stable channels (
- Large/small:
- Large channels (
nixos-17.09,nixos-unstable) provide binary builds for the full breadth of Nixpkgs. - Small channels (
nixos-17.09-small,nixos-unstable-small) are identical to large channels, but contain fewer binaries. This means they update faster, but require more to be built from source.
- Large channels (
https://nixos.org/channels/ hosts the full list of the available official channels is available. Most users will want the stable/large channel, currently nixos-17.09.
Like packages installed via nix-env, channels are managed at user-level. NixOS uses the channels set for the root user to update the system-wide configuration; channels set for other users control only the user environment for that user. If you wish to change the channel used by the system-level configuration (/etc/nixos/configuration.nix), ensure you run the correct nix-channel command as root:
| Listing current channels | nix-channel --list
|
| Adding a primary channel | nix-channel --add https://nixos.org/channels/channel-name nixos
|
| Adding other channels | nix-channel --add https://some.channel/url my-alias
|
| Remove a channel | nix-channel --remove channel-alias
|
| Updating a channel | nix-channel --update channel-alias
|
| Updating all channels | nix-channel --update
|
Note that updating channels won't cause a rebuild in itself; if you want to update channels and rebuild, you can run nixos rebuild --upgrade to do both in one step.
Channel release process
Unstable
The unstable channels (nixpkgs/unstable and nixos/unstable) are built off of the master branch.
Once a PR gets merged, a job is triggered in Hydra. This page lists the 15 most recent builds in the nixpkgs/unstable channel, with the left-most column being the most recent.
A build is considered successful when both of the following two conditions are true:
- All of the jobs in a column are green (meaning, the tests have succeeded)
- All of the jobs in the corresponding evaluation have finished (with a success or a failure)
The evaluation for a build can be found by clicking on the column heading, and then following the the "Part of" link in the "Summary" tab.