anchor.diff:          description = ''
             Whether to synchronise your machine's time using chrony.
             Make sure you disable NTP if you enable this service.
  +        '';
  +      };
  +
  +      package = mkOption {
  +        type = types.package;
  +        default = pkgs.chrony;
  +        defaultText = "pkgs.chrony";
  +        description = ''
  +          Which chrony package to use.
           '';
         };
   
  
positive.code:   config = mkIf cfg.enable {
      meta.maintainers = with lib.maintainers; [ thoughtpolice ];
  
      environment.systemPackages = [ pkgs.chrony ];
  
      users.groups.chrony.gid = config.ids.gids.chrony;
  
  
negative.code: 
  let
    cfg = config.services.chrony;
    chronyPkg = cfg.package;
  
    stateDir = cfg.directory;
    driftFile = "${stateDir}/chrony.drift";
  