anchor.diff:  , iproute, iptables, readline, lvm2, utillinux, systemd, libpciaccess, gettext
   , libtasn1, ebtables, libgcrypt, yajl, pmutils, libcap_ng
   , dnsmasq, libnl, libpcap, libxslt, xhtml1, numad, numactl, perlPackages
  -, curl, libiconv, gmp, xen
  +, curl, libiconv, gmp, xen, zfs
   }:
   # if you update, also bump pythonPackages.libvirt or it will break
   stdenv.mkDerivation rec {
  
positive.code:     "--with-macvtap"
      "--with-virtualport"
      "--with-init-script=redhat"
    ] ++ stdenv.lib.optionals stdenv.isDarwin [
      "--with-init-script=none"
    ];
  
negative.code:     libxslt xhtml1 perlPackages.XMLXPath curl libpcap
    ] ++ stdenv.lib.optionals stdenv.isLinux [
      libpciaccess devicemapper lvm2 utillinux systemd.udev.lib libcap_ng
      libnl numad numactl xen zfs
    ] ++ stdenv.lib.optionals stdenv.isDarwin [
       libiconv gmp
    ];
  