The rc scripts for the beats promise to respect for example the filebeat_conf variable, yet the script itself doesn't. Reproduce by setting filebeat_conf="/root/filebeat.yml" while removing /usr/local/etc/filebeat.yml from the system. Upon starting filebeat using /usr/local/etc/rc.d/filebeat start, a lot of noise will come your way about filebeat not being able to find /usr/local/etc/filebeat.yml.
This functionality made it to upcoming update to 7.9.2 that is going to happen very soon.
I will backport it also to beats6.
(In reply to Juraj Lutter from comment #1)
I'll mark this ticket as Open then. Thanks!