/etc/cloud/cloud.cfg.d/99-rax-openstack-guest-agents.cfg is in rax-nova-agent 2.1.13-0ubuntu3.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 | # Cloud Config for Cloud-init
datasource_list: [ ConfigDrive, None ]
|