anchor.diff:  
     # We need squashfs in the initrd to mount the compressed Nix store,
     # and aufs to make the root filesystem appear writable.
  -  boot.extraModulePackages = (pkgs.lib.optional 
  +  boot.extraModulePackages = (optional 
       (! config.boot.kernelPackages.kernel.features ? aufs) 
       config.boot.kernelPackages.aufs);
     boot.initrd.extraKernelModules = ["aufs" "squashfs"];
  
positive.code:       '';
      };
  
      isoImage.volumeID = pkgs.lib.mkOption {
        default = "NIXOS_BOOT_CD";
        description = ''
          Specifies the label or volume ID of the generated ISO image.
  
negative.code:         source = pkgs.runCommand "empty" {} "ensureDir $out";
          target = "/nix/store";
        }
      ];
  
    # The Grub menu.
  