anchor.diff:      # virtual device), start dhclient after xend.
       jobs.dhclient.startOn = mkOverride 50 "started xend";
   
  +    environment.etc =
  +      [ { source = xendConfig;
  +          target = "xen/xend-config.sxp";
  +        }
  +        { source = "${xen}/etc/xen/scripts";
  +          target = "xen/scripts";
  +        }
  +      ];
  +
  +    # Xen provides udev rules.
  +    services.udev.packages = [ xen ];
  +
  +    services.udev.path = [ pkgs.bridge_utils pkgs.iproute ];
  +
     };
   
   }
  
positive.code: 
    config = mkIf cfg.enable {
  
      environment.systemPackages = [ pkgs.xen ];
  
      # Domain 0 requires a pvops-enabled kernel.
      boot.kernelPackages = pkgs.linuxPackages_2_6_32_xen;
  
      boot.kernelModules = [ "xen_evtchn" "xen_gntdev" ];
  
      # The radeonfb kernel module causes the screen to go black as soon
      # as it's loaded, so don't load it.
  
negative.code: 
  with pkgs.lib;
  
  let 
  
    cfg = config.virtualisation.xen; 
  
    xen = pkgs.xen;
  
    xendConfig = pkgs.writeText "xend-config.sxp"
      ''
        (loglevel DEBUG)
        (network-script network-bridge)
        (vif-script vif-bridge)
      '';
  
  in
  
  {
    ###### interface
  