I got a running production system and under [Server Config] -> [Firewall], it is pointing to "bastille". The "System" -> "Firewall" is empty in ispconfig now. I already have a firewall setup manually by ufw. What exactly can I do from preventing ispconfig from changing my firewall setting? I am afraid ispconfig somehow will trigger the changes by "resync" or if accidentally clicking the "System" -> "Firewall". What will happen if I click save in "Server Config" now if I change the [Firewall] setting from "bastille" to "ufw"?
Nothing, because ISPConfig is not doing that anyway unless you add a firewall under System > Firewall in ISPConfig. Nothing will change unless you use ISPConfig firewall under system > Firewall.