Comment 6 for bug 974584

Sorry, the workaround I listed above was for precise, and actually was incomplete (you also need to ln -s /run/shm $rootfs/dev/shm).

For older releases, the /run transition was not done, so /dev/shm is supposed to be mounted by mountall through /lib/init/fstab. So the workaround is to add a dev/shm entry to /var/lib/lxc/<container>/fstab, or to add it to /var/lib/lxc/<container>/rootfs/lib/init/fstab.lxc.