[openstack-dev] [cinder] [nova] Do we need a "force" parameter in cinder "re-image" API?

Matt Riedemann mriedemos at gmail.com
Tue Oct 9 14:16:16 UTC 2018

On 10/9/2018 8:04 AM, Erlon Cruz wrote:
> If you are planning to re-image an image on a bootable volume then yes 
> you should use a force parameter. I have lost the discussion about this 
> on PTG. What is the main use cases? This seems to me something that 
> could be leveraged with the current revert-to-snapshot API, which would 
> be even better. The flow would be:
> 1 - create a volume from image
> 2 - create an snapshot
> 3 - do whatever you wan't
> 4 - revert the snapshot
> Would that help in your the use cases?

As the spec mentions, this is for enabling re-imaging the root volume on 
a server when nova rebuilds the server. That is not allowed today 
because the compute service can't re-image the root volume. We don't 
want to jump through a bunch of gross alternative hoops to create a new 
root volume with the new image and swap them out (the reasons why are in 
the spec, and have been discussed previously in the ML). So nova is 
asking cinder to provide an API to change the image in a volume which 
the nova rebuild operation will use to re-image the root volume on a 
volume-backed server. I don't know if revert-to-snapshot solves that use 
case, but it doesn't sound like it. With the nova rebuild API, the user 
provides an image reference and that is used to re-image the root disk 
on the server. So it might not be a snapshot, it could be something new.




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