You can use a clientsettings.cfg file to tell clients to use automatic relay selection at install time. You can also use the same file to point them at a specific relay in the case of manual selection. You can even define a failover relay that will be tried if the other settings for automatic or manual relay selection fail. The client will always try the root server as a last resort regardless of any other settings.
I’m not sure if it is clientsettings.cfg is the correct option for linux or not.
Here is part of the settings I use in my clientsettings.cfg file as an example:
Also, see this: https://github.com/jgstew/tools/blob/master/bash/install_bigfix.sh