Coming back to a security bug there is a change in nova [1] in Stein to change the value on the "os_compute_api:servers:create:zero_disk_flavor" policy rule to make it admin-only by default. This makes server create fail for non-admins users who are using flavors with root_gb=0 *unless* they are booting from volume. If you already have this configuration set before upgrading to stein then your deployment tooling shouldn't overwrite the configured policy and you won't notice any changes, but if you have an empty policy file and upgrade and have 0 root_gb flavors, your users could see server create failures. Let us know if you have any issues with this, or would like to see something done in the way of further documentation/communication and/or a nova-status upgrade check. [1] https://review.openstack.org/#/c/603910/ -- Thanks, Matt