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Snapshotting ephemeral disks?

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lars at seas

Aug 16, 2012, 6:58 AM

Post #1 of 4 (250 views)
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Snapshotting ephemeral disks?

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?

--
Lars Kellogg-Stedman <lars [at] seas> |
Senior Technologist | http://ac.seas.harvard.edu/
Academic Computing | http://code.seas.harvard.edu/
Harvard School of Engineering and Applied Sciences |

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vishvananda at gmail

Aug 16, 2012, 5:11 PM

Post #2 of 4 (235 views)
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Re: Snapshotting ephemeral disks? [In reply to]

On Aug 16, 2012, at 6:58 AM, Lars Kellogg-Stedman <lars [at] seas> 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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lars at seas

Aug 17, 2012, 1:00 PM

Post #3 of 4 (234 views)
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Re: Snapshotting ephemeral disks? [In reply to]

> 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.

That looks like it would get us where we want to be. My main goal is
to have a relatively easy process for someone without administrative
access to the host to...

- Uploading an ISO image.
- Boot an instance from that image.
- Install an OS onto something.
- Transform <something> from the previous step into a deployable
image.

Allowing images booted from an ISO to have an attached, snapshottable
root drive would certainly work.

--
Lars Kellogg-Stedman <lars [at] seas> |
Senior Technologist | http://ac.seas.harvard.edu/
Academic Computing | http://code.seas.harvard.edu/
Harvard School of Engineering and Applied Sciences |

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vishvananda at gmail

Aug 17, 2012, 1:26 PM

Post #4 of 4 (235 views)
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Re: Snapshotting ephemeral disks? [In reply to]

On Aug 17, 2012, at 1:00 PM, Lars Kellogg-Stedman <lars [at] seas> wrote:

>> 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.
>
> That looks like it would get us where we want to be. My main goal is
> to have a relatively easy process for someone without administrative
> access to the host to...
>
> - Uploading an ISO image.
> - Boot an instance from that image.
> - Install an OS onto something.
> - Transform <something> from the previous step into a deployable
> image.
>
> Allowing images booted from an ISO to have an attached, snapshottable
> root drive would certainly work.

+1000

Jk0, are you planning on bringing back your patch?

Vish
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