I have created a HA cluster with two opnsense Firewalls. It works fine so far.
Now I'm facing the problem that it might happen that settings are changed on the firewall while the main is down. I do some settings automated via api access and they need to be done on both. Is there any possibility to share the settings from the backup to the main when the main comes back up?
No, the failover design is:
Unit1 sync to Unit2, if Unit1 is down, no changes. If you need to make changes, do them, when restoring Unit1 disable HAsync there and enable HAsync from Unit2 to Unit1. After sync you can reverse the sync order.