[libvirt-users] libvirt live migration, qcow2 image, nbd server

Hi all, When I live migrate a vm using "migrate --live --copy-storage-all mig-vm qemu+ssh://192.168.1.3/system tcp://192.168.1.3" I got the following error WARNING: Image format was not specified for 'nbd://node2:49155/drive-virtio-disk0' and probing guessed raw. 258 Automatically detecting the format is dangerous for raw images, write operations on block 0 will be restricted. 259 Specify the 'raw' format explicitly to remove the restrictions.

From the error itself, I can tell that nbd server treat this image as raw, rather than qcow2. My platform is libvirt+qemu. the image type of this vm is indeed qcow2. I do not know how to let nbd know this image format.

Thanks! Ed