[CRIU] LXC DUMP ERROR

[Serge Hallyn]

Quoting riya khanna (riyakhanna1983 at gmail.com):
> Container's init process mounts its own / as shared (rec).

Ok, so it's outside the purview of lxc.

> So host's / has nothing to do with it.

Ok - there's no inherent reason that would've been the case, so thanks for
the info.

Criu should be able to tell by /proc/$$/mountinfo that the sharing is
purely internal to the container, so it should be able to handle this
eventually.  But in the meantime having your init not make / shared
seems a decent solution.

(If sharing had managed to leak into the container - which lxc tries to
stop - then it would be more complicated for criu)

> On Thu, Oct 2, 2014 at 1:14 PM, Serge Hallyn <serge.hallyn at ubuntu.com> wrote:
> > I don't see "shared rec" anywhere in the criu source.
> >
> > is your / shared on your host?  What does 'grep shared /proc/self/mountinfo'
> > show both in the host and in the container?
> >
> > Quoting riya khanna (riyakhanna1983 at gmail.com):
> >> So I face this error if the container's init mounts / as shared
> >>
> >> "mount rootfs rootfs / shared rec"
> >>
> >>
> >> On Thu, Oct 2, 2014 at 11:02 AM, Serge Hallyn <serge.hallyn at ubuntu.com> wrote:
> >> > Quoting Tycho Andersen (tycho.andersen at canonical.com):
> >> >> On Thu, Oct 02, 2014 at 06:47:28PM +0400, Pavel Emelyanov wrote:
> >> >> > On 10/02/2014 06:46 PM, Tycho Andersen wrote:
> >> >> > > On Thu, Oct 02, 2014 at 06:28:48PM +0400, Pavel Emelyanov wrote:
> >> >> > >> On 09/30/2014 08:42 PM, riya khanna wrote:
> >> >> > >>> What is needed to add support for shared mounts. What could cause
> >> >> > >>> checkpointing of shared mounts to fail? Even I'm facing the same
> >> >> > >>> issue. Thanks!
> >> >> > >>
> >> >> > >> Tycho, I guess these are shared with smth on host, right? I.e.
> >> >> > >> the mount points are "external" from CRIU's perspective.
> >> >> > >
> >> >> > > I guess so, although I don't know for sure (maybe Serge knows?). Is
> >> >> > > this something that criu can handle with --ext-mount-map?
> >> >> >
> >> >> > If the root of the bind mount is sitting outside of the container's
> >> >> > root, then yes :) This is what the --ext-mount-map was designed for.
> >> >>
> >> >> Ok, cool.
> >> >>
> >> >> > > If so, perhaps we could have lxc-checkpoint detect those somehow and tell
> >> >> > > criu.
> >> >> >
> >> >> > Why detect? I thought lxc knows all external bind-mounts it creates.
> >> >>
> >> >> Yes, maybe detect is the wrong word. lxc-checkpoint needs to inspect
> >> >> the config and then tell criu about this.
> >> >
> >> > If this is about the /dev/lxc/ttyN, then those are files bind mounted
> >> > from the host's (or parent container's) /dev/pts/M.  And no, lxc does
> >> > not keep track of the bind mounts it creates.  However, Tycho and I
> >> > have discussed the /dev/lxc/ttyN issue and I'm pretty sure he knows what
> >> > to do.
> >> >
> >> > -serge
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