anchor.diff:  let
   
     inherit (pkgs) ntp;
  +
  +  cfg = config.services.ntp;
   
     stateDir = "/var/lib/ntp";
   
  
positive.code:     restrict 127.0.0.1
      restrict -6 ::1
  
      ${toString (map (server: "server " + server + " iburst\n") config.services.ntp.servers)}
    '';
  
    ntpFlags = "-c ${configFile} -u ${ntpUser}:nogroup";
  
  in
  
  
negative.code:         description = ''
            The set of NTP servers from which to synchronise.
          '';
        };
  
        extraFlags = mkOption {
          type = types.listOf types.str;
          description = "Extra flags passed to the ntpd command.";
          default = [];
        };
  
      };
  