anchor.diff:          { config, pkgs, ... }:
   
           { services.xserver.enable = true;
  +        
  +          services.xserver.displayManager.slim.enable = false;
  +          services.xserver.displayManager.kdm.enable = true;
  +          services.xserver.displayManager.kdm.extraConfig =
  +            ''
  +              [X-:0-Core]
  +              AutoLoginEnable=true
  +              AutoLoginUser=alice
  +              AutoLoginPass=foobar
  +            '';
  +            
             services.xserver.desktopManager.default = "kde4";
             services.xserver.desktopManager.kde4.enable = true;
  +
  +          services.sshd.enable = true;
   
             users.extraUsers = pkgs.lib.singleton
               { name = "alice";
  
positive.code:               home = "/home/alice";
                createHome = true;
                useDefaultShell = true;
              };
  
            environment.systemPackages = [ pkgs.xorg.xclock pkgs.xorg.xwd ];
  
negative.code: 
        $client->waitForFile("/tmp/.X11-unix/X0");
  
        sleep 60;
  
        print STDERR $client->execute("DISPLAY=:0.0 xwd -root > /hostfs/$ENV{out}/screen.xwd");
      '';
  