[libvirt] A couple of questions on snapshot-create/ snapshot-create-as

Hi (Eric?), I got a couple of questions for 'snapshot-create' / 'snapshot-create-as' : 1/ can '--disk-only' option (when used with virsh snapshot-create-as) be run on an offline guest and generate an 'external snapshot' ? Or a running guest is needed? 2/ Can anyone point me to a bit more verbose info on these below options while creating snapshots? --quiesce quiesce guest's file systems --atomic require atomic operation --reuse-external reuse any existing external files Thanks. /kashyap