anchor.diff:        exportReferencesGraph = [ "closure" metaClosure ];
         postVM = ''
           ${if format == "raw" then ''
  -          mv $diskImage $out/nixos.img
  -          diskImage=$out/nixos.img
  +          mv $diskImage $out/${filename}
           '' else ''
  -          ${pkgs.qemu}/bin/qemu-img convert -f raw -O ${format} $diskImage $out/nixos.${extensions.${format}}
  -          diskImage=$out/nixos.${extensions.${format}}
  +          ${pkgs.qemu}/bin/qemu-img convert -f raw -O ${format} $diskImage $out/${filename}
           ''}
  +        diskImage=$out/${filename}
           ${postVM}
         '';
         memSize = 1024;
  
positive.code:     fakeroot nixos-prepare-root $root ${channelSources} ${config.system.build.toplevel} closure
  
      echo "copying staging root to image..."
      cptofs ${pkgs.lib.optionalString partitioned "-P 1"} -t ${fsType} -i $diskImage $root/* /
    '';
  in pkgs.vmTools.runInLinuxVM (
    pkgs.runCommand name
  
negative.code: with lib;
  
  let
    filename = "nixos." + {
      qcow2 = "qcow2";
      vpc   = "vhd";
      raw   = "img";
    }.${format};
  
    nixpkgs = cleanSource pkgs.path;
  
  