[Lxc-users] Strange heisenbug "no space left on device" errors, leftover ephemeralbind mounts?

[Dan Kegel]

This is probably just a bad dream that will end when I move to
running lxc inside vmware instead of virtualbox.

I'm running Ubuntu 12.04.1 in Virtualbox, and inside that, Ubuntu 10.04 via
lxc-start-ephemeral, and inside that, a buildbot slave.  I'm slowly working my
way through various issues that keep the buildbot from working properly
(most recently, I had to switch to aufs from overlayfs, still need to file
a bug for that).
Now the problem is that inside the container, even though there is lots of
disk space shown via df, I'm getting "no space left on device"
after running "make check" for the project I'm building.
The virtualbox has 2GB ram and 22GB disk space free.
I can trigger the error by running just a little bit of "make check",
but if I try stracing that, the problem doesn't seem to happen.
The other strange thing is that I'm seeing leftover ephemeralbind mounts,
even though the log from lxc-start-ephemeral clearly shows the umount statement.

Both problems are triggered by running the testcase.

Next step: switch to vmware and hope this all goes away.
If it doesn't, then maybe I start looking at that overlayfs bug...