{ pkgs, config, ... }:
{
  config = {
    nix = {
      package = pkgs.lix;

      settings = {
        trusted-users = [
          "root"
          config.marleyos.my.name
        ];

        # Enable flakes.
        experimental-features = [
          "nix-command"
          "flakes"
        ];

        # Set up caches.
        extra-substituters = [
          "https://marleyos.cachix.org"
          "https://nix-community.cachix.org"
        ];

        trusted-public-keys = [
          "cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY="
          "marleyos.cachix.org-1:q2kEtqvS5CoQ8BmKlWOfOnN+fi4gUoSuL6HRKy37eCA="
          "nix-community.cachix.org-1:mB9FSh9qf2dCimDSUo8Zy7bkq5CX+/rkCWyvRCYg3Fs="
        ];

        # Disable that annoying "git tree is dirty" warning.
        warn-dirty = false;

        auto-optimise-store = true;
      };

      # Garbage collection.
      gc.automatic = true;
    };

    nixpkgs.config.import = "${config.xdg.configHome}/nixpkgs/config.nix";

    xdg.configFile."nixpkgs/config.nix".text = # nix
      ''
        {
          allowUnfree = true;
        }
      '';
  };
}