Avoid error during snapshot of ISO booted instance

Fixes bug #1023492

If you boot an instance from an image with disk_format=iso and then
attempt to snapshot (i.e. nova image-create) you currently get a
traceback because we do:

  qemu-img convert -f qcow2 -O iso -s $snap $disk $out

and 'iso' is not a format that qemu-img knows anything about.

When booting the image, we use qemu-img to detect that the file is
a raw image so we avoid having to special case disk_format=iso
there. However, there's no way of avoiding the special casing when
extracting a snapshot.

Note 1 - it's not very clever to take a snapshot of a read-only
disk downloaded from glance and upload it back to glance again.
Adding such smarts would be a nice enhancement.

Note 2 - only the destination format is important here because
we can only be extracting from a qcow2 image since snapshots
only work where use_cow_images=True. See also #1030844.

Change-Id: I21ff6db8ebb59a83d27f224283fb76f582c38a0e

0 files changed, 0 insertions, 0 deletions