The firewall service can provide protection for your RHEL system and services from other hosts on the local network or Internet. Although firewalling is often maintained on the border routers to your network, additional protection can be provided by host-based firewalls, such as the netfilter firewall on the Linux kernel. The netfilter firewall on RHEL 7 can be implemented via the iptables or firewalld service, with the latter being the default.

The status of the firewalld service can be interrogated in a normal manner using the systemctl command. This will provide a verbose output if the service is running. This will include the PID (process ID) of firewalld along with recent log messages. The following is a command extract along with a screenshot of the output from RHEL7.1:

# systemctl status firewalld

If you just need a quick check with a less verbose output, make use of the firewall-cmd command. This is the main administrative tool used to manage firewalld. The -...