In this tutorial, we will show you how to set up a Firewall using FirewallD on CentOS 8. For those of you who didn’t know, Firewalls play a crucial role in protecting your server from unauthorized access and potential threats. CentOS 8, a popular Linux distribution, comes with a powerful and user-friendly firewall management tool called FirewallD.
FirewallD introduces several key concepts that you should be familiar with before proceeding with the configuration. These concepts include zones, services, ports, protocols, and port forwarding.
- Zones
FirewallD uses zones to manage the trust level of network connections. Each zone has its own set of rules that determine which traffic is allowed or denied. CentOS 8 comes with several predefined zones, such as trusted, home, internal, work, public, external, dmz, block, and drop. You can assign network interfaces to specific zones based on your security requirements.
- Services
FirewallD uses the concept of services to represent a collection of ports and protocols that a specific service requires to function properly. CentOS 8 includes a set of predefined services, but you can also create your own custom service definitions to suit your needs.
- Ports, Protocols, and Port Forwarding
FirewallD allows you to open or close specific ports and control traffic based on protocols like TCP, UDP, or ICMP. Additionally, you can configure port forwarding rules to redirect traffic from one port to another, enabling you to run services on non-standard ports while still maintaining security.
- Runtime vs Permanent Configuration
FirewallD distinguishes between runtime and permanent configurations. Runtime configurations are applied immediately but are lost upon reboot, while permanent configurations persist across system restarts. It’s essential to save your runtime configuration to make it permanent.
This article assumes you have at least basic knowledge of Linux, know how to use the shell, and most importantly, you host your site on your own VPS. The installation is quite simple and assumes you are running in the root account, if not you may need to add ‘sudo‘ to the commands to get root privileges. I will show you the step-by-step Setup Firewall using FirewallD on CentOS 8.
Prerequisites
- A server running one of the following operating systems: CentOS 8.
- It’s recommended that you use a fresh OS install to prevent any potential issues.
- SSH access to the server (or just open Terminal if you’re on a desktop).
- A network connection or internet access.
- A
non-root sudo useror access to theroot user. We recommend acting as anon-root sudo user, however, as you can harm your system if you’re not careful when acting as the root.
Setup Firewall using FirewallD on CentOS 8
Step 1. First, let’s start by ensuring your system is up-to-date.
sudo dnf install epel-release sudo dnf update
Step 2. Installing FirewallD on CentOS 8.
Firewalld is installed by default on CentOS 8 system, but if it is not installed on your system, you can execute the following command for its installation:
sudo dnf install firewalld sudo systemctl enable firewalld --now
Enable or disable Firewalld from starting automatically at system boot:
sudo systemctl enable firewalld sudo systemctl start firewalld
Check the current status of Firewalld and see if it’s running:
sudo systemctl status firewalld
Step 3. Setup and configuration of FirewallD.
Below are the predefined zones included in FirewallD:
- drop – Dropped all incoming connections without any reply and only allowed outgoing connections.
- block – It is the same as the zone drop, but all incoming connections are blocked with
icmp-host- prohibitedoricmp6-adm-prohibitedmessages. - public – It represents unreliable public areas.
- external – External networks in the event that the firewall uses as the gateway. Because it is configured for NAT masquerading and internal network will remain private but accessible.
- internal – Only accepted the selected incoming connections and it’s for the internal network.
- DMZ – Demilitarized zone, it is publicly accessible to the internal network with limited access and accepted only selected incoming connections.
- work – Using for work machines.
- home – Using for home machines.
- trusted – Accept all network connections.
By default, the public zone is the default zone after the firewall service is enabled. To list all available zones run:
firewall-cmd --get-zones
The below commands are used to change the default zone and verify.
firewall-cmd --set-default-zone=home firewall-cmd --get-default-zone
For example open HTTP port 80 and HTTPS port 443, and run the commands used to open temporarily:
firewall-cmd --zone=public --add-service=http firewall-cmd --zone=public --add-service=https
Below are commands used to open permanently:
firewall-cmd --zone=public --permanent --add-service=http firewall-cmd --zone=public --permanent --add-service=https
To implement the changes we need to reload the firewall with:
firewall-cmd --reload
Check for open ports/services:
firewall-cmd --list-all
Congratulations! You have successfully configured Firewalld. Thanks for using this tutorial for installing FirewallD on the CentOS 8 system. For additional help or useful information, we recommend you check the official FirewallD website.
