Re: [libvirt-users] Using virsh blockcopy -- what's it supposed to accomplish?

Where are you specifying the format? I have not personally played with NBD much. But here's my guess: Even though /tmp/dsk.test.qcow2 is a qcow2 file, the NBD server is serving up a RAW image through /dev/nbd2. Thus, if you are trying to treat /dev/nbd2 as the destination of your copy, you MUST tell qemu that the file format of the copy is to be raw (regardless of the file format of the original that is being copied from). If you omit the --raw (also spelled --format=raw in newer libvirt) parameter to the virsh blockcopy command, then libvirt has to guess at the destination format; if the source was qcow2, then libvirt will guess that the destination should be qcow2 as well. But writing qcow2 data to a raw NBD disk means you have created a nested file in /tmp/dsk.test.qcow2 - it is a qcow2 file whose contents are a qcow2 file whose contents are the raw data (not typical usage, and a bit weird to wrap your head around).

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