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

[Olivier Nicaise]

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 at 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.
>
> Daniel
> --
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