[Openstack] Snapshotting ephemeral disks?

Vishvananda Ishaya vishvananda at gmail.com
Fri Aug 17 00:11:27 UTC 2012


On Aug 16, 2012, at 6:58 AM, Lars Kellogg-Stedman <lars at seas.harvard.edu> wrote:

> I have a system that I've booted using a live CD image (so
> .../instance-<ID>/disk points at the ISO file).  I've installed an OS
> onto /dev/vda (which is .../instance-<ID>/disk.local).
> 
> Running 'nova image-create <INSTANCE> <NAME>` results in a traceback in
> the compute log:
> 
>  2012-08-16 09:48:56 TRACE nova.rpc.amqp ProcessExecutionError: Unexpected error while running command.
>  2012-08-16 09:48:56 TRACE nova.rpc.amqp Command: qemu-img convert -f qcow2 -O iso -s 6966cceec946407eb12531ddbe7bb7ac /virt/pools/openstack_2/instance-0000004c/disk /tmp/tmpMJ9GuL/6966cceec946407eb12531ddbe7bb7ac
>  2012-08-16 09:48:56 TRACE nova.rpc.amqp Exit code: 1
>  2012-08-16 09:48:56 TRACE nova.rpc.amqp Stdout: ''
>  2012-08-16 09:48:56 TRACE nova.rpc.amqp Stderr: "qemu-img: Unknown file format 'iso'\n"
>  2012-08-16 09:48:56 TRACE nova.rpc.amqp 
> 
> And the image gets stuck in the "SAVING" state:
> 
>    # nova image-list
>    ...
>    | f269eebc-d86e-4cd0-aacc-8b0c53fb3bb2 | cloud-f17-x86_64              | SAVING | 4b3fccf9-28ab-4c29-acdb-cc5c18c862af |
> 
> Is there a way to do this properly?  Obviously I can just munge around
> in the filesystem to do what I want, but I was hoping for something
> more convenient.
> 
> I guess another option would be...
> 
> - Boot from the live CD
> - Create a new volume
> - Attach the volume
> - Install onto the volume
> 
> Is it possible to snapshot an ephemeral disk?

This is not possible. Sounds like you really want a fix for this bug:

https://bugs.launchpad.net/nova/+bug/914484

The fix was reverted but hopefully it can be cleaned up and come back in.

Vish



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