In a site upgraded to Ussuri we are getting faults starting instances
2020-11-30 13:41:40.586 232871 ERROR oslo_messaging.rpc.server libvirt.libvirtError: Requested operation is not valid: format of backing image '/var/lib/nova/instances/_base/xxx' of image '/var/lib/nova/instances/xxx' was not specified in the image metadata (See https://libvirt.org/kbase/backing_chains.html for troubleshooting)
Bug #1864020 reports similar symptoms, where due to an upstream change in Libvirt v6.0.0+ images need the backing format specified.
The fix for Bug #1864020 handles the case for new instances. However, for upgraded instances we're hitting the same problem, as those still don't have backing format specified.
In a site upgraded to Ussuri we are getting faults starting instances
2020-11-30 13:41:40.586 232871 ERROR oslo_messaging. rpc.server libvirt. libvirtError: Requested operation is not valid: format of backing image '/var/lib/ nova/instances/ _base/xxx' of image '/var/lib/ nova/instances/ xxx' was not specified in the image metadata (See https:/ /libvirt. org/kbase/ backing_ chains. html for troubleshooting)
Bug #1864020 reports similar symptoms, where due to an upstream change in Libvirt v6.0.0+ images need the backing format specified.
The fix for Bug #1864020 handles the case for new instances. However, for upgraded instances we're hitting the same problem, as those still don't have backing format specified.