devos/doc/concepts/overrides.md

Overrides

Each NixOS host follows one channel. But many times it is useful to get packages or modules from different channels.

This is what the overrides are for. You can make use of the overrides.nix to override specific packages to be pulled from other channels. Any overlay may get channels as their first argument.

Example

Packages

The override packages are defined as a regular overlay with an extra arguement channels. This refers to all channels defined in flake.nix.

Pulling the manix package from the latest flake:

channels: final: prev: {
  inherit (pkgs.latest) manix;
}

Modules

You can also pull modules from other channels. All modules have access to the modulesPath for each channel as <channelName>ModulesPath. And you can use disabledModules to remove modules from the current channel.

Pulling the zsh module from the latest flake:

{ latestModulesPath }: {
  modules = [ "${latestModulesPath}/programs/zsh/zsh.nix" ];
  disabledModules = [ "programs/zsh/zsh.nix" ];
}

Note:

Sometimes a modules name will change from one branch to another.