[libvirt] [FYI] Skript to extract qcow2 snapshot info to libvirt snapshot xml

[Eric Blake]

On 10/20/2011 02:57 AM, Daniel P. Berrange wrote:
> On Thu, Oct 20, 2011 at 08:50:35AM +0200, Philipp Hahn wrote:
>> Hello,
>>
>> I sometimes get foreign qcow2 images with embedded snapshots. Without the
>> corresponding XML files libvirt doesn't recognize them. Therefor I created
>> the attached script to fake-create the missing snapshot XML files.
>> Be advised that the XML files might not work in all cases, especially when the
>> configuration was changed between snapshots, but at least I prefer a solution
>> working 95% of the times instead of 0% ;-)
>> And since I already wrote it, others might find it useful as well.
>
> I wonder if we ought to put this in the libvirt source tree under
> examples/ or something like that. Or turn it into a proper script
> at tools/virt-qemu-import-snapshots ?

Or even add a flag or new API to the virDomainSnapshot family of 
commands to allow automating this as part of the API.  The only drawback 
of parsing from qcow2 images is that you lack parent information, and 
none of the snapshots get marked current.  Additionally, I already have 
pending on my plate a bug fix - right now, if any of the qcow2 files 
already contain an internal snapshot by a given name, or if you use a 
small integer name, like '1', which conflicts with qcow2 snapshot tag 
numbers, then you can inadvertently overwrite existing snapshots.  So I 
_already_ have to fix the code to parse qemu-img output so as to add a 
safety check that any new internal snapshot name does not collide with 
any already-existing snapshot designations, and it won't be that much 
harder to turn that parsing into to something permanent.

But yes, thanks for the script, and I'll probably be referring to it in 
my snapshot improvements in some form or another (whether it remains an 
external script or becomes part of the internal libvirtd C code for the 
qemu driver).

-- 
Eric Blake   eblake at redhat.com    +1-801-349-2682
Libvirt virtualization library http://libvirt.org