The issue has shown up in regular-*-20130207: /etc/resolv.conf
would suddenly be empty upon successful bootup in virtualbox
with a single DHCP configurable ethernet.

dmesg has some trouble signs:

  aufs au_lkup_neg:267:kworker/0:2[998]:
  I/O Error, resolv.conf should be negative on b0

sem@ tells something like that has been seen before in a different
configuration (multiple aufs overlays with /etc/ and /var sitting
in different ones resulting in broken hardlinks); rescue boot with
a test "echo > /etc/resolv.conf" yields an I/O error either.

The patch is loosely based upon livecd-net-eth and
m-p-d::profiles/live/image-scripts.d/init3-{network,resolve}.

See also #28484 for the (still ongoing) discussion.