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
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
-
Linux Mint 22.2 Beta Available for Testing
Some interesting new additions and improvements are coming to Linux Mint. Check out the Linux Mint 22.2 Beta to give it a test run.
-
Debian 13.0 Officially Released
After two years of development, the latest iteration of Debian is now available with plenty of under-the-hood improvements.
-
Upcoming Changes for MXLinux
MXLinux 25 has plenty in store to please all types of users.
-
A New Linux AI Assistant in Town
Newelle, a Linux AI assistant, works with different LLMs and includes document parsing and profiles.
-
Linux Kernel 6.16 Released with Minor Fixes
The latest Linux kernel doesn't really include any big-ticket features, just a lot of lines of code.
-
EU Sovereign Tech Fund Gains Traction
OpenForum Europe recently released a report regarding a sovereign tech fund with backing from several significant entities.
-
FreeBSD Promises a Full Desktop Installer
FreeBSD has lacked an option to include a full desktop environment during installation.
-
Linux Hits an Important Milestone
If you pay attention to the news in the Linux-sphere, you've probably heard that the open source operating system recently crashed through a ceiling no one thought possible.
-
Plasma Bigscreen Returns
A developer discovered that the Plasma Bigscreen feature had been sitting untouched, so he decided to do something about it.
-
CachyOS Now Lets Users Choose Their Shell
Imagine getting the opportunity to select which shell you want during the installation of your favorite Linux distribution. That's now a thing.