anchor.diff:  
             echo "exporting VirtualBox VM..."
             mkdir -p $out
  -          fn="$out/nixos-${config.system.nixos.label}-${pkgs.stdenv.system}.ova"
  +          fn="$out/${cfg.vmFileName}"
             VBoxManage export "$vmName" --output "$fn"
   
             rm -v $diskImage
  
positive.code:           VBoxManage internalcommands createrawvmdk -filename disk.vmdk -rawdisk $diskImage
  
            echo "creating VirtualBox VM..."
            vmName="NixOS ${config.system.nixos.label} (${pkgs.stdenv.system})"
            VBoxManage createvm --name "$vmName" --register \
              --ostype ${if pkgs.stdenv.system == "x86_64-linux" then "Linux26_64" else "Linux26"}
            VBoxManage modifyvm "$vmName" \
              --memory 1536 --acpi on --vram 32 \
              ${optionalString (pkgs.stdenv.system == "i686-linux") "--pae on"} \
              --nictype1 virtio --nic1 nat \
              --audiocontroller ac97 --audio alsa \
  
negative.code:           The size of the VirtualBox base image in MiB.
          '';
        };
        memorySize = mkOption {
          type = types.int;
          default = 1536;
          description = ''
            The amount of RAM the VirtualBox appliance can use in MiB.
          '';
        };
        vmDerivationName = mkOption {
          type = types.str;
          default = "nixos-ova-${config.system.nixos.label}-${pkgs.stdenv.system}";
          description = ''
            The name of the derivation for the VirtualBox appliance.
          '';
        };
        vmName = mkOption {
          type = types.str;
          default = "NixOS ${config.system.nixos.label} (${pkgs.stdenv.system})";
          description = ''
            The name of the VirtualBox appliance.
          '';
        };
        vmFileName = mkOption {
          type = types.str;
          default = "nixos-${config.system.nixos.label}-${pkgs.stdenv.system}.ova";
          description = ''
            The file name of the VirtualBox appliance.
          '';
        };
      };
    };
  
    config = {
      system.build.virtualBoxOVA = import ../../lib/make-disk-image.nix {
        name = cfg.vmDerivationName;
  
        inherit pkgs lib config;
        partitionTableType = "legacy";
  