anchor.diff:        diskImage=$(pwd)/disk-image.qcow2
         origImage=${attrs.diskImage}
         if test -d "$origImage"; then origImage="$origImage/disk-image.qcow2"; fi
  -      qemu-img create -b "$origImage" -f qcow2 $diskImage
  +      ${kvm}/bin/qemu-img create -b "$origImage" -f qcow2 $diskImage
   
         echo "$buildCommand" > cmd
   
  
positive.code:   createEmptyImage = {size, fullName}: ''
      mkdir $out
      diskImage=$out/disk-image.qcow2
      qemu-img create -f qcow2 $diskImage "${toString size}M"
  
      mkdir $out/nix-support
      echo "${fullName}" > $out/nix-support/full-name
  
negative.code:     fi
      diskImage="$1"
      if ! test -e "$diskImage"; then
        ${kvm}/bin/qemu-img create -b ${image}/disk-image.qcow2 -f qcow2 "$diskImage"
      fi
      export TMPDIR=$(mktemp -d)
      export out=/dummy
  