anchor.diff:  
           path = 
             [ pkgs.bridge_utils pkgs.gawk pkgs.iproute pkgs.nettools 
  -            pkgs.utillinux pkgs.bash pkgs.xen pkgs.pciutils pkgs.procps
  +            pkgs.utillinux pkgs.bash xen pkgs.pciutils pkgs.procps
             ];
   
  -        preStart = "${pkgs.xen}/sbin/xend start";
  +        preStart = "${xen}/sbin/xend start";
   
  -        postStop = "${pkgs.xen}/sbin/xend stop";
  +        postStop = "${xen}/sbin/xend stop";
         };
   
       # To prevent a race between dhclient and xend's bridge setup
  
positive.code: 
  with pkgs.lib;
  
  let cfg = config.virtualisation.xen; in
  
  {
    ###### interface
  
negative.code: 
    config = mkIf cfg.enable {
  
      environment.systemPackages = [ xen ];
  
      # Domain 0 requires a pvops-enabled kernel.
      boot.kernelPackages = pkgs.linuxPackages_2_6_32_xen;
  
      boot.kernelModules = [ "xen_evtchn" "xen_gntdev" "xen_blkback" "xen_netback" "xen_pciback" "blktap" ];
  
      # The radeonfb kernel module causes the screen to go black as soon
      # as it's loaded, so don't load it.
  