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: 
  with pkgs.lib;
  
  let cfg = config.virtualisation.xen; in
  
  {
    ###### interface
  
negative.code: 
      system.extraSystemBuilderCmds =
        ''
          ln -s ${xen}/boot/xen.gz $out/xen.gz
          echo "${toString cfg.bootParams}" > $out/xen-params
        '';
  
  