nixos/modules/nix.nix

inputs: {
  lib,
  self,
  settings,
  ...
}: {
  nix = {
    #   package = nix.packages.${pkgs.system}.nix;
    #automatically get registry from input flakes
    registry = (
      lib.attrsets.mapAttrs (
        _: value: {
          flake = value;
        }
      ) (
        lib.attrsets.filterAttrs (
          _: value: (
            !(lib.attrsets.hasAttrByPath ["flake"] value) || value.flake == false
          )
        )
        inputs
      )
      // {
        nixpkgs.flake = inputs.unstable;
        system.flake = self;
      }
    );
    #automatically add registry entries to nixPath
    nixPath = (lib.mapAttrsToList (name: value: name + "=" + value) inputs) ++ ["system=${self}" "nixpkgs=${inputs.unstable}"];
    settings = {
      experimental-features = ["nix-command" "flakes" "repl-flake"];
      auto-optimise-store = true;
      warn-dirty = false;
      flake-registry = builtins.toFile "empty-flake-registry.json" ''{"flakes":[],"version":2}'';
      keep-outputs = true;
      keep-derivations = true;
      trusted-users = [
        "root"
        "@wheel"
      ];
      allowed-users = [
      ];
    };
  };
  environment.etc."booted-system".source = self;
}