libvirt users - Jul 2015 - Hot Cloning - clone running Virtual Machines

Greetings,

I am running a test automation service which makes use of QEMU/KVM. As the
tests run for few minutes, the time spent booting the OS (Windows) is quite
a waste of resources so I decided to play a bit around the idea of hot
cloning running VMs.

Following an old discussion I found, I proceeded with saving the VM state
through virsh save, edit its XML file with virsh save-image-edit and
restore it through virsh restore.

The problem comes when I try to change some specific fields in the XML. As
I run several instances on the same server, I need to provide different
names and UUIDs to avoid collisions. Unfortunately, libvirt forbids this
operation issuing the following error message:

error: unsupported configuration: Target domain uuid
7c85e288-88fe-43d2-8b9c-89af4c83c10a does not match source
62f28517-8601-4d2e-942c-a20d087f9f4a

Same thing applies with the name field.

Is this a limitation of the API or it is a designed protection mechanism?
Would it be possible to overcome this limit?

Thank you.

On Mon, Jul 20, 2015 at 03:58:26PM +0300, NoxDaFox
wrote:
> Greetings,
> 
> I am running a test automation service which makes use of QEMU/KVM. As the
> tests run for few minutes, the time spent booting the OS (Windows) is quite
> a waste of resources so I decided to play a bit around the idea of hot
> cloning running VMs.
> 
> Following an old discussion I found, I proceeded with saving the VM state
> through virsh save, edit its XML file with virsh save-image-edit and
> restore it through virsh restore.
> 
> The problem comes when I try to change some specific fields in the XML. As
> I run several instances on the same server, I need to provide different
> names and UUIDs to avoid collisions. Unfortunately, libvirt forbids this
> operation issuing the following error message:
> 
> error: unsupported configuration: Target domain uuid
> 7c85e288-88fe-43d2-8b9c-89af4c83c10a does not match source
> 62f28517-8601-4d2e-942c-a20d087f9f4a
> 
> Same thing applies with the name field.
> 
> Is this a limitation of the API or it is a designed protection mechanism?
> Would it be possible to overcome this limit?
Cloning running VMs is explicitly not supported because there is no
practical way to safely update guest OS state that must remain unique
(eg encryption keys, unique identifiers, etc) nor update hardware that
has unique properties (eg BIOS UUID, NIC mac address, and more), nor
deal with things like established network connections

Regards,
Daniel
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