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Cant export volume snapshot as Image

asked 2016-06-14 09:33:56 -0500

DaveJ gravatar image

I want to back up some vms externally. I used to do this by snapshotting and saving the image from glance. When I used volume backed instances this doesn't seem to work.

I have deployed Openstack with Cinder. When I boot an instance, I select boot from image (Creates new volume)

After making changes to the instance, I hit create snapshot. This creates a snapshot visible under the volumes page in horizon, and also creates an entry in the glance image list.

If I try to save/export that image from glance I get a file with 0 bytes i.e.

openstack image save 84b481fe-aeec-4d36-9ebd-8e2df286c82c --file /tmp/test.img ls -l /tmp/test

Is this a bug with cinder ? Or am I missing some vital command or flag?

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answered 2016-06-16 02:31:47 -0500

eblock gravatar image

There was a bug regarding the launch of a snapshot of a volume backed instance: https://bugs.launchpad.net/horizon/+bug/1374931

One comment says

Per the discussion in gerrit, the zero-byte snapshot is normal from nova/glance, as it reflects the fact that no space is being taken in glance, since the volume snapshots are stored in cinder.

Depending on your storage backend you could retrieve that image, e.g. if you are using Ceph you could export the respective image with rbd commands. Ii seems there is currently no way to download a volume backed snapshot except with some workarounds, I may be wrong though.

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Asked: 2016-06-14 09:33:56 -0500

Seen: 1,706 times

Last updated: Jun 16 '16