I am currently having an issue with the libvirt_lxc binary that is launched when starting a lxc instance using libvirt. This process seems to have its own namespace for mounts. 

What happens is that if I umount something in the global namespace, it stays mounted in the libvirt_lxc namespace.

I'm working with drbd, and after unmounting the mount point, I want to change the state of the drbd resource as Secondary. But if fails. Indeed, libvirt_lxc has still the resource which is mounted in its namespace.

Currently, I wanted to test the setns tool to enter the namespace and umount the mount point. But I am currently on Ubuntu 12.04 with a 3.2.0-59 kernel which does not have /proc/[pid]/ns/mnt

I can't upgrade to 3.8 (which have the proc mnt file) as the drbd tools are not compatible.

Do you have an idea of what I could try ?

Here I the steps I do to reproduce the issue:

- Mount a drbd file system

- Start a lxc instance with libvirt

- Umount the drbd file system

- Set the drbd resource as secondary. => Does not work