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Re: [libvirt-users] libvirt_lxc namespace and umount in global namespace

Thanks for your fast feedback!

I created the bug: https://bugzilla.redhat.com/show_bug.cgi?id=1067489

2014-02-20 15:03 GMT+01:00 Daniel P. Berrange <berrange redhat com>:
On Thu, Feb 20, 2014 at 01:47:52PM +0100, Olivier Nicaise wrote:
> Hi,
> 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 ?

Ahh, interesting scenario that I'd not considered. With LXC there are
in fact 3 mounts namespaces in play

 - The host OS namespace
 - The libvirt_lxc namespace
 - The actual container namespace

The libvirt_lxc namespace is basically the same as the host namespace,
but with the addition of a devpts for the container's /dev/pts.

We explicitly don't allow dynamic changes to propagate from the host
OS to the container namespace, however, it sounds like we *should*
allow host OS changes to propagage to the libvirt_lxc process
namespace. Can you file a bug about this, so it doesn't get forgotten.

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