anchor.diff:  
   rec {
   
  -  qemu = pkgs.qemu_kvm;
  +  qemu = buildPackages.qemu_kvm;
   
     modulesClosure = makeModulesClosure {
       inherit kernel rootModules;
  
positive.code:   hd = "vda"; # either "sda" or "vda"
  
    initrdUtils = runCommand "initrd-utils"
      { buildInputs = [ nukeReferences ];
        allowedReferences = [ "out" modulesClosure ]; # prevent accidents like glibc being included in the initrd
      }
      ''
  
negative.code:   rpmClosureGenerator =
      {name, packagesLists, urlPrefixes, packages, archs ? []}:
      assert (builtins.length packagesLists) == (builtins.length urlPrefixes);
      runCommand "${name}.nix" {
        nativeBuildInputs = [ buildPackages.perl buildPackages.perlPackages.XMLSimple ];
        inherit archs;
      } ''
        ${lib.concatImapStrings (i: pl: ''
          gunzip < ${pl} > ./packages_${toString i}.xml
        '') packagesLists}
  