anchor.diff:  
     package = pkgs.openntpd_nixos;
   
  -  cfgFile = pkgs.writeText "openntpd.conf" ''
  +  configFile = ''
       ${concatStringsSep "\n" (map (s: "server ${s}") cfg.servers)}
       ${cfg.extraConfig}
     '';
  
positive.code:     # Add ntpctl to the environment for status checking
      environment.systemPackages = [ package ];
  
      users.extraUsers = singleton {
        name = "ntp";
        uid = config.ids.uids.ntp;
  
negative.code:       type = with types; lines;
        default = "";
        example = ''
          listen on 127.0.0.1
          listen on ::1
        '';
        description = ''
          Additional text appended to <filename>openntpd.conf</filename>.
  