snapshot=on fails with non file-based storage

[Richard Jones]

The snapshot=on option doesn't work with an nbd block device:

/usr/bin/qemu-system-x86_64 \
[...]
    -device virtio-scsi-pci,id=scsi \
    -drive file=nbd:localhost:61930,snapshot=on,format=raw,id=hd0,if=none \
    -device scsi-hd,drive=hd0 \
[...]

gives the error:

qemu-system-x86_64: -drive file=nbd:localhost:61930,snapshot=on,format=raw,id=hd0,if=none: could not open disk image nbd:localhost:61930: No such file or directory

If you remove the snapshot=on flag, it works (although that of course means that the block device is writable which we don't want).

Previously reported here:

  http://permalink.gmane.org/gmane.comp.emulators.qemu/148390

and I can confirm this still happens in qemu 1.4.0.

[Thomas Huth (th-huth)]

Triaging old bug tickets... I think this has likely been fixed in 2013 ... or can you still reproduce this issue with the latest version of QEMU? Could we close this ticket nowadays?

[Richard Jones (rjones-redhat)]

Let's close this. libguestfs doesn't use snapshot=on any longer.