If you want to stay up to date with a set of packages, it’s not very convenient to manually download the latest set of Nix expressions for those packages and upgrade using nix-env. Fortunately, there’s a better way: Nix channels. A Nix channel is just a URL that points to a place that contains a set of Nix expressions and a manifest. Using the command nix-channel you can automatically stay up to date with whatever is available at that URL. You can “subscribe” to a channel using nix-channel --add, e.g., $ nix-channel --add https://nixos.org/channels/nixpkgs-unstable subscribes you to a channel that always contains that latest version of the Nix Packages collection. (Subscribing really just means that the URL is added to the file ~/.nix-channels, where it is read by subsequent calls to nix-channel --update.) You can “unsubscribe” using nix-channel --remove: $ nix-channel --remove nixpkgs To obtain the latest Nix expressions available in a channel, do $ nix-channel --update This downloads and unpacks the Nix expressions in every channel (downloaded from url/nixexprs.tar.bz2). It also makes the union of each channel’s Nix expressions available by default to nix-env operations (via the symlink ~/.nix-defexpr/channels). Consequently, you can then say $ nix-env -u to upgrade all packages in your profile to the latest versions available in the subscribed channels.