1{den, ...}: {
 2  den.aspects.core.includes = [den.aspects.core.nh];
 3  den.aspects.core.nh = {
 4    nixos = {
 5      programs.nh = {
 6        enable = true;
 7        clean.enable = true;
 8        clean.extraArgs = "--keep-since 4d --keep 3";
 9      };
10
11      system.tools = {
12        # disable useless tools
13        nixos-build-vms.enable = false;
14        nixos-enter.enable = false;
15        nixos-generate-config.enable = false;
16        nixos-install.enable = false;
17        nixos-option.enable = false;
18        nixos-rebuild.enable = false; # No needed, use `nh os` instead.
19      };
20    };
21  };
22}