firewall-cmd --get-active-zones ``` This command gets the active zone(s). Now, apply port rules to the relevant zones returned above. For example if the zone is `public`, use ```sh firewall-cmd --zone=public --add-port=9000/tcp --permanent ``` Note that `permanent` makes sure the rules are persistent across firewall start, restart or reload. Finally reload the firewall for changes to take effect. ```sh firewall-cmd --reload ``` ### iptables For hosts with iptables enabled (RHEL, CentOS, etc), you...