Comment 21 for bug 1334398

After looking a little bit more (at' _live_snapshot' function in Nova[*]) , the below seem to be the precise equivalent sequence of (libvirt) operations of what's happening in Nova's '_live_snapshot' function. Thanks to libvirt developer Eric Blake for reviewing this:

(0) Take the Libvirt guest's XML backup:

    $ virsh dumpxml --inactive vm1 > /var/tmp/vm1.xml

(1) Abort any failed/finished block operations:

    $ virsh blockjob vm1 vda --abort

(2) Undefine a running domain. (Note: Undefining a running domain does not _kill_ the domain, it just converts it from persistent to
      transient.)

    $ virsh undefine vm1

(3) Invoke 'virsh blockcopy' (This will take time, depending on the size of disk image vm1):

    $ virsh blockcopy \
        --domain vm1 vda \
        /export/backups/vm1-copy.qcow2 \
        --wait \
        --verbose

(4) Abort any failed/finished block operations: (as Dan pointed out in comment #17, this the abort operation where QEMU
    might be failing):

    $ virsh blockjob vm1 vda --abort

   NOTE: If we use '--finish' command in step 3 it is equivalent to the
   above command (consequently, step 4 can be skipped).

(5) Define the guest again (to make it persistent):

    $ virsh define /var/tmp/vm1.xml

(6) From the obtained new copy, convert the QCOW2 with a backing file to a flat (raw) image with no backing file:

    $ qemu-img convert -f qcow2 -O raw vm1.qcow2 conv-vm1.img

Notes (from Eric Blake):
    The _live_snapshot function concludes it all with redefining the
    domain (umm, that part looks fishy in the code - you undefine it
    only if it was persistent, but redefine the domain unconditionally;
    so if you call your function on a domain that is initially
    transient, you end up with a persistent domain at the end of your
    function).

  [*] https://github.com/openstack/nova/blob/master/nova/virt/libvirt/driver.py#L1593