I think I have seen this in previous bugs. Trying to live backup qcow2 images. I am able to virsh snapshot-create-as and virsh domblklist shows correct new source, but I am unable to commit back changes to qcow base. I get the above error.

Libvirt at 1.2.2-0ubuntu13.1.17

Qemu is (2.0.0+dfsg-2ubuntu1.22)

I tried compiling latest libvirt, but cannot get it to connect to socket on installed binaries

Anyone get this working on Ubuntu 14.04?