Either the fully qualified domain name (FQDN), or just the host name if it does not exist. This is a convenience option for modules to read instead of fqdn when a mere hostName is also an acceptable value; this option does not throw an error when domain or fqdn is unset.

if config.networking.domain != null || config.networking.fqdn is set then config.networking.fqdn else config.networking.hostName