Re: [libvirt-users] Mounting VM filesystem on host while VM running

On 08.08.2016 09:33, Patrick PICHON wrote: > Hello, > > > All my VMs are using LVs created on the host side. > > I'm using collectd to monitor some of the ressources of my host as well > as the libvirt pluging to monitor my VMs. > > Collectd has an interesting plugin ( df ) which can monitor the > filesystem usage. > > I would like to use it to monitor the VMs filesytsem usage. > > As it is obvious that if I mount the VM filesystem on the host while the > VM is running, I'm wondering if I could mount it in READONLY without > expecting any panic/corruption problem. > > > Any advices ? I don't think it is a good idea. Mostly because of caching - you probably won't get consistent results. Moreover, some filesystems (e.g. ext4) replay journal even if mounted as RO (frankly, I haven't found a way how to mount ext really RO). I don't know of any filesystem that would support being mounted multiple times from two different hosts (except network FS obviously).

What you could do is to write small guest agent that will report disk usage to host (e.g. via virito serial console).