nix-channel 1 Nix nix-channel manage Nix channels nix-channel --add url name --remove name --list --update names --rollback generation A Nix channel is 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 both a set of Nix expressions and a pointer to a binary cache. See also . 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), makes them the default for nix-env operations (by symlinking them from the directory ~/.nix-defexpr), and performs a nix-pull on the manifests of all channels to make pre-built binaries available. --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. 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.nixpkgsVersion' "14.04.527.0e935f1" $ nix-channel --rollback switching from generation 483 to 482 $ nix-instantiate --eval -E '(import <nixpkgs> {}).lib.nixpkgsVersion' "14.04.526.dbadfad" /nix/var/nix/profiles/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/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. 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 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”. binary-cache-url A file containing the URL to a binary cache (such as https://cache.nixos.org. Nix will automatically check this cache for pre-built binaries, if the user has sufficient rights to add binary caches. For instance, in a multi-user Nix setup, the binary caches provided by the channels of the root user are used automatically, but caches corresponding to the channels of non-root users are ignored. Binary caches can be created and maintained using nix-push. MANIFEST.bz2 (Deprecated in favour of binary caches.) A manifest as created by nix-push. Only used if binary-cache-url is not present or if the nix.conf option force-manifest is set.