Name

       nix-channel - manage Nix channels

Synopsis

       nix-channel {--add url [name] | --remove name | --list | --update [names…] | --rollback [generation] }

Description

       A Nix channel is a mechanism that allows you to automatically stay up-to-date with a set of pre-built Nix
       expressions. A Nix channel is just a URL that points to a place containing a set of Nix expressions.

       To see the list of official NixOS channels, visit https://nixos.org/channels.

       This command has the following operations:

       • --add url [name]
         Adds  a  channel  named  name  with  URL url to the list of subscribed channels. If name is omitted, it
         defaults to the last component of url, with the suffixes -stable or -unstable removed.

       • --remove name
         Removes the channel named name from the list of subscribed channels.

       • --list
         Prints the names and URLs of all subscribed channels on standard output.

       • --update [names…]
         Downloads the Nix expressions of all subscribed channels (or only those included in names if specified)
         and makes them the default for nix-env operations  (by  symlinking  them  from  the  directory  ~/.nix-
         defexpr).

       • --rollback [generation]
         Reverts  the  previous  call  to  nix-channel  --update. Optionally, you can specify a specific channel
         generation number to restore.

       Note that --add does not automatically perform an update.

       The list of subscribed channels is stored in ~/.nix-channels.

Examples

       To subscribe to the Nixpkgs channel and install the GNU Hello package:

       $ nix-channel --add https://nixos.org/channels/nixpkgs-unstable
       $ nix-channel --update
       $ nix-env -iA nixpkgs.hello

       You can revert channel updates using --rollback:

       $ nix-instantiate --eval -E '(import <nixpkgs> {}).lib.version'
       "14.04.527.0e935f1"

       $ nix-channel --rollback
       switching from generation 483 to 482

       $ nix-instantiate --eval -E '(import <nixpkgs> {}).lib.version'
       "14.04.526.dbadfad"

Files

       • /nix/var/nix/profiles/per-user/username/channels
         nix-channel uses a nix-env profile to keep track of previous versions of the subscribed channels. Every
         time you run nix-channel --update, a new channel generation (that is, a  symlink  to  the  channel  Nix
         expressions  in  the  Nix  store) is created. This enables nix-channel --rollback to revert to previous
         versions.

       • ~/.nix-defexpr/channels
         This is a symlink to /nix/var/nix/profiles/per-user/username/channels. It ensures that nix-env can find
         your channels. In a multi-user installation, you  may  also  have  ~/.nix-defexpr/channels_root,  which
         links to the channels of the root user.

Channel format

       A channel URL should point to a directory containing the following files:

       • nixexprs.tar.xz
         A  tarball containing Nix expressions and files referenced by them (such as build scripts and patches).
         At the top level, the tarball should contain a single directory. That directory  must  contain  a  file
         default.nix that serves as the channel’s “entry point”.

                                                                                                  nix-channel(1)