Daniel P. Berrange: > http://libvirt.org/formatstorage.html#StorageVolBacking > > This is currently support for Cow, QCow, QCow2, VMDK and LVM storage > types. Some of these allow for the underling backing store to be > writable, others require that its readonly. I tried the following under libvirt 0.6.0: vol = pool.createXML("""<volume type="block"> <name>hurgle</name> <capacity>2147483648</capacity> <backingStore> <path>/dev/VMs/test-disk</path> <format>raw</format> </backingStore> </volume>""", 0) It promptly created a volume, but not as a copy-on-write snapshot: "dmsetup ls --target snapshot" shows nothing, and the image has none of the data from the test-disk volume. The pool I used to create these volumes is clearly LVM: virsh # pool-dumpxml VMs <pool type='logical'> <name>VMs</name> <uuid>bde8f8ed-7e65-8323-ea93-51223d86fedd</uuid> <capacity>66433581056</capacity> <allocation>2281701376</allocation> <available>64151879680</available> <source> <name>VMs</name> <format type='lvm2'/> </source> <target> <path>/dev/VMs</path> <permissions> <mode>0700</mode> <owner>0</owner> <group>0</group> </permissions> </target> </pool> You mentioned some constraints about permissions earlier, but I would have expected that to raise an exception--vol is a valid volume object and I can query it and mkfs it and so forth. The test-disk volume is completely quiescent and unmounted. Do I need to prepare it in some other way to make it suitable for livirt to use as the base of a snapshot? (Just for sanity's sake, I verified that libvirt.getVersion() returns 6000) -- "Forget the damned motor car Nick Moffitt and build cities for lovers and friends." nick@xxxxxxxx -- Lewis Mumford -- Libvir-list mailing list Libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list