Bug#800845: autopkgtest: Add support for nested VMs

[martin.pitt@ubuntu.com (Martin Pitt)]

Hello again,

Martin Pitt [2016-03-09  8:52 +0100]:
> > I get (w/ qemu-system 1:2.5+dfsg-4~bpo8+1) with current git master
> > (no changes):
> > mount: /dev/vdb1 is write-protected, mounting read-only
> > 
> > So I can't really reproduce it. :-(
> 
> I now get the same. I must have wrecked something on Monday, I figure.

I'm not hallucinating after all. I just tried this again:

  ./run-from-checkout tests/testpkg-simple/ --shell --- qemu adt-xenial-amd64-cloud.img

Then ssh'ed in, and ran

  sudo apt-get install -y kpartx
  sudo kpartx -av /dev/baseimage
  sudo mount /dev/mapper/baseimage1 /mnt
  (no "readonly" warning here)
  sudo touch /mnt/foo
  (succeeded!)
  ls -l /mnt/foo
  -rw-r--r-- 1 root root 0 Mar  9 08:22 /mnt/foo

However, "foo" does not actually appear on the underlying image, so
maybe it's sometimes using the overlay or something.
So whatever it is, it doesn't actually seem to modify the baseimage,
so we can ignore that for now.

Martin

-- 
Martin Pitt                        | http://www.piware.de
Ubuntu Developer (www.ubuntu.com)  | Debian Developer  (www.debian.org)