anchor.diff:        default = false;
         description = ''
           Whether to enable the DHCPv${postfix} server.
  -      '';
  -    };
  -
  -    stateDir = mkOption {
  -      type = types.path;
  -      # We use /var/lib/dhcp for DHCPv4 to save backwards compatibility.
  -      default = "/var/lib/dhcp${if postfix == "4" then "" else postfix}";
  -      description = ''
  -        State directory for the DHCP server.
         '';
       };
   
  
positive.code: 
    imports = [
      (mkRenamedOptionModule [ "services" "dhcpd" ] [ "services" "dhcpd4" ])
    ];
  
    ###### interface
  
  
negative.code: 
    config = mkIf (cfg4.enable || cfg6.enable) {
  
      systemd.services = dhcpdService "4" cfg4 // dhcpdService "6" cfg6;
  
    };
  