So far, we've looked at iptables, a generic firewall management system that's available on all Linux distros, and ufw, which is available for Debian/Ubuntu-type systems. For our next act, we turn our attention to firewalld, which is the default firewall manager on Red Hat Enterprise Linux 7/8 and all of their offspring.
But here's where things get a bit confusing. On RHEL/CentOS 7, firewalld is implemented differently from the way it is on RHEL/CentOS 8. That's because, on RHEL/CentOS 7, firewalld uses the iptables engine as its backend. On RHEL/CentOS 8, firewalld uses nftables as its backend. Either way, you can't create rules with normal iptables or nftables commands because firewalld stores the rules in an incompatible format.
Until very recently, firewalld was only available for RHEL 7/8 and their offspring. Now, however...
