Open Stack

On 3/30/17 1:48 AM, Massimo Sgaravatto wrote:
> Thanks a lot
> 
> Aren't there problems to change the type of an image (qcow2 --> raw) if
> there are VMs instantiated using that image ?

I missed the image conversion part.  Glance doesn't allow you (even an
admin) to change the checksum of an image.  So even though it will let
you add a location of arbitrary image data, you won't be able to change
the checksum, and hence any consumer who does compare the checksum of
the received data with the 'checksum' field on the Image record in
Glance will detect a mismatch and reject the image.

I think the VM problem would be limited to doing a rebuild, but the
checksum problem I outlined above is enough reason not to do this.  Off
the top of my head, I'd suggest using image metadata to correlate the
"old" and "new" images.

(As far as why Glance allows you to add locations of data that doesn't
match the checksum of the existing image ... well, I believe one of the
original use cases for multiple image locations was that the data might
not be available to Glance at the time the location was set, and since
consumers should always verify their downloads, this wasn't thought to
be a problem.)

cheers,
brian