1{
 2  flake.modules.nixos.core = _: {
 3    programs.nh = {
 4      enable = true;
 5      clean.enable = true;
 6      clean.extraArgs = "--keep-since 4d --keep 3";
 7    };
 8
 9    system.tools = {
10      # disable useless tools
11      nixos-build-vms.enable = false;
12      nixos-enter.enable = false;
13      nixos-generate-config.enable = false;
14      nixos-install.enable = false;
15      nixos-option.enable = false;
16      nixos-rebuild.enable = false; # No needed, use `nh os` instead.
17    };
18  };
19}