[openstack-dev] [Nova] Libvirt - updates backing file permission of qcow2 image on launching instance

Agrawal, Ankit Ankit11.Agrawal at nttdata.com
Tue Jun 30 07:48:41 UTC 2015

Hi All,

I am trying to fix a race condition between imagebackend and imagecache in nova (openstack) while creating an instance using qcow2 image backend. On creating a qcow2 image libvirt stores the base/backing file path reference while copying the image at instance disk info. While spawning the instance nova usage this base file reference as a backing file to launch instance.

When base file is created in nova image cache directory its owner is set to openstack (a nova user) but on launching the instance from guest.launch, libvirt updates the base/backing file owner from openstack to libvirt-qemu which causes permission error if we try to use that base file later.

Can someone please help me to understand why libvirt is updating the owner of base file stored in image cache directory, is it a bug in libvirt or the expected behaviour?

Thanks & Regards,
Ankit Agrawal

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