We recently ran into libvirt lxc shutdown failing because of mount namespaces not being available:

# virsh -c lxc:/// start test01
Domain test01 started
 
# virsh -c lxc:/// list
 Id    Name                           State
----------------------------------------------------
 9336  test01                         running
 
# virsh -c lxc:/// shutdown test01
error: Failed to shutdown domain test01
error: Mount namespaces are not available on this platform: Function not implemented
 
/var/log/libvirt/libvirtd.log:
2014-09-03 15:50:50.682+0000: 3030: error : virProcessRunInMountNamespace:999 : Mount namespaces are not available on this platform: Function not implemented

We're running Debian wheezy with stock libc6 2.13-38, a custom 3.12.15 kernel (with namespace support) and libvirt 1.2.3.

The patch in this previous thread fixes shutdown for us and we'd like to see it merged upstream:

https://www.redhat.com/archives/libvir-list/2014-May/msg00175.html

Thanks,
Steve