Comment 4 for bug 1023492

Reviewed: https://review.openstack.org/10530
Committed: http://github.com/openstack/nova/commit/af0651946010e6bcc966005aa9fc2a1f38d3748a
Submitter: Jenkins
Branch: master

commit af0651946010e6bcc966005aa9fc2a1f38d3748a
Author: Mark McLoughlin <email address hidden>
Date: Mon Jul 30 13:03:39 2012 +0100

    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