Re: [libvirt] Mount events are not propagated to namespaces

On Fri, Jun 16, 2017 at 10:01:26AM +0200, Michal Privoznik wrote: > Dear list, > > while trying to fix a bug of mine, I've realized the mounts are not > being propagated into qemu namespaces once domains are running. That is, > imagine you have a domain running and then you plug in a flash disk, > mount it into host, because you have a file there that you want to > hotplug as a disk to your domain. You're not hotplugging the whole flash > disk, but a file on it. Problem is, that the mount event of the flash > disk is not propagated to qemu namespace even though the root is > remounted as MS_SLAVE|MS_REC right after the namespace is created. > > After some digging. I am able to reproduce this even without libvirt at all: > > # mount --make-rshared / > # mount | grep floppy > <empty/> > # unshare -m /bin/bash > # mount --make-rslave / The problem here is your 'unshare' command, which mounts '/' as private, and it appears the later '--make-rslave' is unable to undo this.

If you use unshare -m --propagation slave /bin/sh then the example works correctly.