anchor.diff:  
       system.extraSystemBuilderCmds =
         ''
  -        ln -s ${xen}/boot/xen.gz $out/xen.gz
  +        ln -s ${pkgs.xen}/boot/xen.gz $out/xen.gz
           echo "${toString cfg.bootParams}" > $out/xen-params
         '';
   
  
positive.code:       message = "Xen currently does not support EFI boot";
      } ];
  
      virtualisation.xen.stored = mkDefault "${xen}/bin/oxenstored";
  
      environment.systemPackages = [ xen ];
  
      # Make sure Domain 0 gets the required configuration
      #boot.kernelPackages = pkgs.boot.kernelPackages.override { features={xen_dom0=true;}; };
  
negative.code: 
  
      environment.etc =
        [ { source = "${pkgs.xen}/etc/xen/xl.conf";
            target = "xen/xl.conf";
          }
          { source = "${pkgs.xen}/etc/xen/scripts";
            target = "xen/scripts";
          }
        ];
  
      # Xen provides udev rules.
      services.udev.packages = [ pkgs.xen ];
  
      services.udev.path = [ pkgs.bridge-utils pkgs.iproute ];
  
  