How to set up a firewall in Linux

Use firewalld or iptables to secure Linux; firewalld is user-friendly with zones and services, ideal for CentOS/RHEL/Fedora, while iptables offers granular control for Debian/Ubuntu. Enable firewalld: sudo systemctl start firewalld, allow services like SSH with --add-service=ssh, or open ports via --add-port=8080/tcp, then reload rules. For iptables, allow loopback, established connections, and specific ports (22, 80), set default DROP policy, and save rules to persist. Always limit open ports, use SSH keys, and test firewall with tools like nmap. Regularly review rules using firewall-cmd --list-all or iptables -L. Prefer firewalld for simplicity, iptables for control.

Setting up a firewall in Linux is essential for securing your system from unauthorized access and network threats. The most common way to manage a firewall on Linux is through iptables or the newer firewalld, depending on your distribution. Below are practical steps to set up a basic firewall using both methods.

Using firewalld (Recommended for CentOS, RHEL, Fedora)

firewalld is user-friendly and uses zones and services, making it easier to manage firewall rules.

Using iptables (Common in Debian, Ubuntu, and older systems)

iptables gives you fine-grained control over packet filtering but requires more detailed commands.

Basic Security Tips

A good firewall setup balances accessibility and protection.

Mostly, use firewalld if your system supports it—it’s simpler and well-integrated. For more control or on older systems, iptables is reliable. Either way, having a configured firewall is a critical step in securing your Linux server. Basically, start with allowing essential services and block the rest.

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