[lxc-users] after stopping container, mountpoint is still there

[Serge Hallyn]

Quoting Florian Klink (flokli at flokli.de):
> Hi,
> 
> I have the problem that filesystems mounted with lxc.hook.pre-mount stay
> mounted the whole time, even after the container is stopped.
> 
> According to my understandinding, mountpoints mounted by these hook
> scripts will be private to the container and cleaned up on container
> stop automatically (man lxc.container.conf):
> 
> lxc.hook.pre-mount
> A  hook to be run in the container's fs namespace but before the rootfs
> has been set up. This allows for manipulation of the rootfs, i.e. to
> mount an encrypted filesystem. Mounts done in this hook will not be
> reflected on the host (apart from mounts propagation), so they will be
> automatically cleaned up when the container shuts down.
> 
> 
> 
> However, I can see them when running `df` or `mount` on the host, and
> they stay mounted even when the container is stopped (which creates
> weird errors when you try to start the container again).
> 
> 
> A bit more information about my setup:
> 
> Arch Linux amd64, systemd 211, kernel 3.13.6
> 
> I created an archlinux "base image"
> (using pacstrap -d /path/to/base-image base base-devel), and union-mount
> it together with a cow/ directory to the new root.
> 
> The hook looks similar to the provided "hooks/mountecryptfsroot":
> 
> mount-aufs:
> 
> #!/bin/sh
> LXC_COW_PATH=$(echo $LXC_ROOTFS_PATH | sed 's/root$/cow/')
> mount -n -t aufs none ${LXC_ROOTFS_PATH} -o br=${LXC_COW_PATH}=rw:$1=ro
> 
> 
> container config:
> 
> [...]
> lxc.autodev = 1
> lxc.hook.pre-mount = /var/lib/lxc/container-name/mount-aufs
> /path/to/base/image
> lxc.rootfs = /var/lxc/containers/container-name/root
> [...]
> 
> 
> 
> I also tried to hook an lxc.hook.post-stop script that umounts it, but
> that's also working not reliable...
> 
> 
> Is this intended behaviour or a bug?

Sounds like your / is shared.  (grep shared /proc/self/mountinfo).
Perhas you can just 'mount --make-rslave /' at the top of
the pre-mount hook.