Partly following up this message: https://www.redhat.com/archives/libvirt-users/2011-October/msg00142.html > > And what about qemu's option "snapshot=on" ? > > Unreliable. It won't work with SELinux (since qemu tries to create the > snapshot on /tmp), and it makes your guest unmigratable. I think that > it is easier to have libvirt use qemu-img to create a qcow2 wrapper > prior to booting the guest, at which point the solution is easier to > control from an sVirt perspective, and is more likely to allow us to > figure out a way to make things work with migration (at least, I'm > hoping I can figure out how to migrate a guest with a transient disk). Lack of this feature is pretty annoying, particularly since (a) libguestfs needs it and (b) it's a trivial patch to add snapshot=on to the qemu driver. So to concentrate on the two objections above: - Why is SELinux concerned about qemu creating and using a file in /tmp? Obviously it should stop qemu opening and reading random files from /tmp but that would be a different rule surely? - The documentation actually states that using <transient/> may make your guest unable to migrate, and in any case we don't care. > But if you want to use qemu's snapshot=on in the meantime, you can > use the <qemu:commandline> namespace XML to add it. Is there an example how to do this? It seems like it might be possible using a global qemu '-set device.<id>.snapshot=on' parameter, but how can I know what <id> libvirt will give to a '-drive' parameter? (I found from experimentation that it's something like "drive-virtio-disk0", but I can't track down the bit of code that produces this string yet ...) Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming blog: http://rwmj.wordpress.com Fedora now supports 80 OCaml packages (the OPEN alternative to F#) http://cocan.org/getting_started_with_ocaml_on_red_hat_and_fedora -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list