Nix/doc/manual/src/command-ref/nix-channel.md

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.

  A channel URL must point to a directory containing a file nixexprs.tar.gz. At the top level, that tarball must contain a single directory with a default.nix file that serves as the channel’s entry point.

• --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.

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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"