Comment 9 for bug 1969971

The nova-cloud-controller charm will create hostname, fqdn and ip address entries for each compute host. It does using settings 'private-address' and 'hostname' on the cloud-compute relation. private-address will be the address resolvable from libvirt-migration-network (if configured) otherwise the unit private-address.

Here comes the problem; the hostname added to known_hosts will be from relation 'hostname' BUT the hostname fqdn will be resolved from private-address. This means that if Nova compute is configured to use network X for the its management network and libvirt-migration-network is set to a different network, the fqdn in known_hosts will be from the latter. This is all good until nova-compute needs to do a vm resize and the image used to build the vm no longer exists in Glance. At which point Nova will use the instance.hostname from the database to perform an scp from source to destination and this fails because this hostname (fqdn from management network) is not in known_hosts.

This is something that Nova should ultimately have support for but in the interim the suggestion is that nova-cloud-controller always adds the management network fqdn to known_hosts.