Bug#773881: live-boot: Fails to boot with union=overlayfs

[intrigeri@debian.org]

Package: live-boot
Version: 4.0.2-1
Severity: normal

Hi,

I've tried booting a Wheezy system (live-boot 3.x) with Linux 3.18
from experimental, udev from wheezy-backports (Wheezy's udev isn't
supported by this new kernel), and union=overlayfs.

I'm manually had the overlay module included into the initramfs, to
workaround the other bug I've just reported.

Boots fails and I get dropped into the initramfs emergency shell, for 
various reasons:

  * first, "mount -t overlayfs" is called, while it should be
    "mount -t overlay"
  * second, we try to mount the "${UNIONTYPE}" (aka. "overlayfs")
    device, which fails: it should be "overlay"
  * third, the call to mount lacks the workdir= option.

I've verified that the source code in the debian-next branch is
affected as well (but not tested in practice, which seemed futile
given the code hasn't changed). I may work on a fix soonish, but don't
hold your breathe.

It seems that the code would be simpler if we accepted union=overlay
instead of union=overlayfs. Can we do that? Non-experimental Debian
kernels have never supported overlayfs yet, so that should be
fine, no?

Cheers,
--
intrigeri