Quick notes on Linux RedHat/Centos firewalld service. From the curriculum of RH134 and Red Hat Certified Systems Administrator (RHCSA)

1. If you need more?
organized with zones
runtime - permanent
firewall-config (GUI) - reload to take changes
firewall-cmd --help
netfilter controll
iptables or firewalld
base install (not minimal)
if interface doesn't match any zone default will be used
/urs/lib/firewalld/services (predefined services)
/etc/firewalld/ - manual config with files
Logs : /var/log/firewalld
Example:
firewall-cmd --permanent --zone=public --add-service=mysql
Firewalld basic use
Firewalld Page 1

2. If you need more?
rich rules:
firewall-cmd --permanent --zone=public --add-rich-rule='
rule family="ipv4"
source address="1.2.3.4/32"
port protocol="tcp" port="4567" accept'
Firewalld Page 2