Firewall management
Getting to Know firewalld
© Lead Image © Gino Santa Maria, Fotolia.com
Managing a firewall can be a hassle, but it's worse to manage a breach because you didn't have one.
Afirewall is an important part of a security strategy. However, it is only one component and not a security panacea for reasons that will become clear later in this article. A host-based firewall protects the local system just as a network firewall protects an entire network or part of a network, such as a DMZ.
On CentOS 7 and newer, Red Hat Enterprise Linux 7 and newer, and Fedora 18 and newer, the default firewall is firewalld (see the "Features" box for more information.) If you use a Red Hat-based distribution, then you probably have it already. If you use other distributions, firewalld is available via git and as a tarball [1]. Firewalld uses zones to define trust levels of network connections or interfaces. (Zones are an advanced topic not covered in this article; look for a future article covering firewalld zones).
Troubleshooting Firewalls
Sys admins of all skill levels have wasted countless hours troubleshooting a problem that ended up pointing to a firewall that has prevented remote access to a service. The term "remote" is important. Firewalls don't prevent access to local services; firewalls prevent access from remote systems across the network but not access from the local system itself. The point of a firewall is to deny everything from the outside except what you specifically allow in. Unfortunately, frustration with firewall rules often ends in the firewall being disabled by an otherwise well-meaning sys admin.
[...]
Buy this article as PDF
(incl. VAT)
Buy Linux Magazine
Subscribe to our Linux Newsletters
Find Linux and Open Source Jobs
Subscribe to our ADMIN Newsletters
Digital Autonomy
• The Answer Was Already on the Shelf
• Changing the Chip Industry: How Public Investment Has Grown Open Silicon
• United Nations Open Source Portal Goes Live
• EU Open Source Strategy Plays Key Role in Tech Sovereignty Package
• France Says “Au Revoir” to Microsoft
Support Our Work
Linux Magazine content is made possible with support from readers like you. Please consider contributing when you’ve found an article to be beneficial.
News
-
2,000 Vulnerabilities per Linux Release
Thanks to AI bug hunters, the Linux kernel is seeing record numbers of vulnerabilities, and it's overwhelming developers.
-
Linux Exempt from California’s Age Verification Law
So long as Linux is distributed under the GPL, MIT, BSD, and Apache licenses, the OS is exempt from being required to verify the age of its users in California.
-
Roll Out the Cake: Linux Turns 35
35 years ago, a Finnish student began a humble project that would forever change the course of technology.
-
China Switching from Windows to Linux
China has ordered several government agencies to drop a Chinese-developed version of Windows 10 in favor of either KylinOS or UOS.
-
Pine64 Halts Production of Linux Devices
With continued DRAM and eMMC shortages, Pine64 has decided to discontinue production of Linux devices.
-
The Bullet-Proof KDE Software Initiative Is Coming
KDE, Techpaladin, and Kubuntu Focus have announced a new initiative that will provide at least three years of support for KDE Plasma 6.6 LTS and related software.
-
Linux Mint Shares a Possible Kernel Cleanup Solution
For those on Linux Mint who like to keep multiple kernels around but don't want them to take up too much space, you might be getting a new automated tool.
-
CachyOS Gets an Update
CachyOS August 2026 release is now available with the latest version of KDE, some new features, and plenty of improvements.
-
The Linux Kernel Dev Staging Area Now Rejects AI-Generated Patches
Unless a kernel patch is a valid security fix, it will be rejected if it was created using AI.
-
Linux Surpasses Double-Digit Market Share
According to two sources, the Linux operating system has hit a major milestone in market share that naysayers thought would never happen.