{pkgs, ...}: {
  nix = {
    package = pkgs.lixPackageSets.stable.lix;

    # automatic cleanup
    gc = {
      automatic = true;
      dates = "weekly";
      options = "--delete-older-than 21d";
    };

    settings = {
      # builders-use-substitutes = true;
      experimental-features = ["nix-command" "flakes"];
      flake-registry = "/etc/nix/registry.json";

      keep-derivations = true;
      keep-outputs = true;

      trusted-users = ["root" "@wheel"];
      substituters = ["https://cache.nixos.org/"];
    };
  };

  nixpkgs = {
    config.allowUnfree = true;
    config.permittedInsecurePackages = [
      "nixos-config"
      "electron-36.9.5"
      "dotnet-sdk-6.0.428"
      "olm-3.2.16"
    ];
  };
}