anchor.diff:  
     qemuCommandLinux = ''
       ${qemuProg} \
  -      -enable-kvm \
         ${lib.optionalString (pkgs.stdenv.system == "x86_64-linux") "-cpu kvm64"} \
         -nographic -no-reboot \
         -virtfs local,path=/nix/store,security_model=none,mount_tag=store \
  
positive.code: 
  rec {
  
    kvm = pkgs.qemu;
  
    qemuProg = "${kvm}/bin/qemu-system-" + (if stdenv.system == "x86_64-linux" then "x86_64" else "i386");
  
  
    modulesClosure = makeModulesClosure {
  
negative.code:     fi
      diskImage="$1"
      if ! test -e "$diskImage"; then
        ${qemu}/bin/qemu-img create -b ${image}/disk-image.qcow2 -f qcow2 "$diskImage"
      fi
      export TMPDIR=$(mktemp -d)
      export out=/dummy
  