[lxc-devel] Strange problem (stray mounts) with lxc-create...

[Serge Hallyn]

Quoting Michael H. Warfield (mhw at WittsEnd.com):
> On Wed, 2013-10-09 at 09:50 -0500, Serge Hallyn wrote: 
> > > lxc-create -n Ubuntu-test -t ubuntu
> > > 
> > > Bingo...
> > > 
> > > /dev/mapper/fedora-root on /usr/lib64/lxc/rootfs type ext4 (rw,relatime,seclabel,data=ordered)
> > > 
> > > Why is lxc-create even creating that mount?  I don't see any reason for
> > 
> > Check lxccontainer.c:785 and line 805.  We call bdev_mount() in case its
> > a blockdev.  In the case of a dir-backed container we still end up doing
> > a bind mount of the rootfs.
> > 
> > > it.  We're never running the container in lxc-create.  Running
> > > "umount /usr/lib64/lxc/rootfs" clears it and we're off to the races
> > > again.
> > > 
> > > If I were to venture a WAG (Wild Ass Guess) some initialization code is
> > > creating that bind mount that is not needed and that the cleanup code in
> > > lxc-create is unaware of.  But I haven't gone to the trouble of trying
> > > to track the code down yet.
> 
> > Now is your / still MS_SHARED?  The bdev create and templates
> > run in a private namespace, but if MS_SHARED then the mounts get
> > bounced back to host.  Maybe we need to manually set MS_PRIVATE every
> > time after doing an unshare() in lxc code.
> 
> It doesn't seem to be...  Am I looking in the right spot.  I don't see
> it in the options...
> 
> [root at hydra mhw]# mount | grep ' / '
> /dev/mapper/fedora-root on / type ext4 (rw,relatime,seclabel,data=ordered)

What does /proc/self/mountinfo on the host looks like?