I am trying to perform a blockpull on an attached disk, but I cannot do
this using "virsh attach-disk" specifying a new, empty overlay file created
with "qemu-img create". The VM does not pick up the backing_file path from
the qcow2 overlay file, and there seems to be no way to specify the backing
path through the attach-disk command itself. Instead the backing path has
to be specified in the xml file used to create the VM, which precludes
attaching a new disk to a running VM. Is this a bug? Is it possible to
attach a disk to a running VM, and specify its backing path, using qemu
directly? This is with qemu 4.2.0 and libvirt 6.0.0.
