[libvirt-users] Spawn new domains from a snapshot.

NoxDaFox noxdafox at gmail.com
Fri May 25 13:48:01 UTC 2012

Hello everybody,

I would like to be able to spawn several domains from a given snapshot.

Here's a possible scenario:
-  I start from disk image A.qcow2.
-  I made some changes to A and I take different snapshots: 1 - 2 - 3
-  While A is still running I would like to run domains B and C from snapshot 2
I don't want to revert a domain, I want to create new ones. The
original should be still running but it may be stopped if necessary.

The idea I had was to create a qcow2 image through qemu-img (let's
call it Z.qcow2), as I'm using copy on write for performances then I'd
need to commit the changes contained in Z to A always using qemu-img.
Is there any other better way? I would love to do it through libvirt,
maybe specifying in the config file the backing store path of the
whole disk and then giving as a source file the one containing deltas.

This could be a good idea for realizing a cloud based system as a
incredible amount of time would be saved though it.
Imagine moving only qcow2 file containing deltas through the network
and then give the base image to each node so that it can use it for
start it's own domain.
As well would be possible to store the heavy base image in a single
node saving storage space.
Lots of cpu cycles saved once new image versions must be deployed
(typical case a windows update to propagate in the nodes network).


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