centos 7 firewall

Introduction

As one of the most popular Linux distributions, CentOS 7 is widely used in servers and desktop computers. In order to protect the system and data, it is crucial to configure the firewall properly. This article will discuss the basics of CentOS 7 firewall, its components, and how to manage it.

Firewall Components

The firewall on CentOS 7 is composed of two main components: the iptables service and the firewalld service. The iptables service is a traditional Linux firewall that uses a set of rules to filter network traffic. It is powerful and versatile, but it can be difficult to manage for beginners. The firewalld service is a newer firewall that provides a more user-friendly interface for managing the firewall. It uses zones, services, and rules to control network access.

Firewall Zones

Firewall zones are a key concept in firewalld on CentOS 7. A zone is a predefined set of rules that determine how the firewall should behave when traffic is coming from or going to a specific source. There are several built-in zones in firewalld, such as public, private, internal, and trusted. Each zone has its own set of rules that define which types of traffic are allowed or denied.

Firewall Services

A service is a predefined set of rules that allow or deny specific network traffic. Firewalld on CentOS 7 comes with a large number of predefined services, such as SSH, HTTP, FTP, and DNS. When a service is enabled for a zone, the firewall allows or denies traffic based on the rules of the service. If a service is not predefined, it can be manually defined using custom rules.

Managing the Firewall

There are several ways to manage the CentOS 7 firewall. The most basic method is to use the firewall-cmd command-line tool. It allows you to add, remove, or modify rules, zones, and services. For example, to add a new rule to allow incoming SSH traffic, you can use the following command: firewall-cmd --zone=public --add-service=ssh --permanent

Another way to manage the firewall is to use the graphical user interface (GUI) provided by firewalld. The GUI allows you to view and edit the zones, services, and rules in a more intuitive way. To use the GUI, you need to install the firewall-config package and run the firewall-config command.

Conclusion

The firewall is an essential part of the security of any CentOS 7 system. By configuring the firewall properly, you can prevent unauthorized access to your network and protect your data from malicious attacks. Understanding the components and features of the CentOS 7 firewall is the first step towards effective firewall management.