Linux Server Operating Systems: Red Hat Enterprise Linux and Beyond

A few years back, things were relatively simple regarding Red Hat Enterprise Linux (RHEL). If you needed support, you’d get a contract with Red Hat. If you didn’t, you’d run the community RHEL distro, Community Enterprise Operating system (CentOS).

Things have changed.

First, Red Hat had long known that most RHEL-family customers were using the free CentOS rather than paying for RHEL.  So, back in 2011, Red Hat incorporated its own patches directly into its kernel tree. All the code’s still in there, but, as one person said then, “It’s sort of like asking someone for a recipe for the family’s chocolate chip cookies and getting cookie batter instead.”

That didn’t stop groups and companies like Oracle, which had been copycatting RHEL in its Oracle Linux since 2006, from making their own RHEL clone cookies.

In 2014, Red Hat “adopted” CentOS, hoping to convert its users into RHEL customers. That didn’t work. So in 2020, Red Hat changed CentOS from being a stable RHEL clone to being a rolling Linux release distro, CentOS Stream. That’s not the same thing at all. As one user said, “The use case for CentOS is completely different than CentOS Stream. Many, many people use CentOS for production enterprise workloads, not for dev. CentOS Stream might be OK for dev/test, but it is unlikely people are going to adopt CentOS Stream for prod.”

And, indeed, the company didn’t. Instead, two leading Linux developers, CloudLinux founder and CEO Igor Seletskiy and CentOS founder and CIQ CEO Gregory Kurtzer, responded by creating new RHEL clones, AlmaLinux and Rocky Linux, respectively.

Both these new RHEL clones have commercial support. CloudLinux, which is a business RHEL clone designed for shared hosting providers, offers technical support for AlmaLinux, while CIQ offers support for Rocky Linux. Third-party Linux consulting companies, such as Perforce OpenLogic, also provide support.

But, if you have in-house Linux expertise, you don’t need to pay for it. Both AlmaLinux and Rocky Linux are governed by non-profit foundations. AlmaLinux is run by the AlmaLinux OS Foundation, and Rocky Linux is governed by the  Rocky Enterprise Software Foundation (RESF).

That’s where things sat until the summer of 2023. Red Hat restricted the use of its RHEL code. This made it much harder for any of the RHEL cloners to create their takes on this operating system.

That hasn’t stopped them, though. AlmaLinux decided it would no longer build its distribution off RHEL’s code; instead, it would use CentOS Stream’s code for its foundation. The others took a more aggressive path. Oracle trash-talked Red Hat and vowed to maintain RHEL compatibility. The RESF would use other methods to get the RHEL code. And, then, in a surprise move, the European Linux power SUSE decided it would fork RHEL as Liberty Linux.

If that sounds like a lot of duplication of effort to you, it did to several of these groups as well. So, three of them — CIQ, Oracle and SUSE — formed the Open Enterprise Linux Association (OpenELA). Their united goal was to foster “the development of distributions compatible with Red Hat Enterprise Linux (RHEL) by providing open and free enterprise Linux source code.”

That means there won’t be an OpenELA binary distribution. Instead, it will release a freely available, redistributable and maintained GitHub Enterprise Linux (EL) compatible source code repository.

Today, from Red Hat, we have RHEL 9.3, the original, and CentOS Stream, which is a development distribution set midstream between Fedora Linux and RHEL. Generally speaking, CentOS is not for production.

On the other side, we have AlmaLinux 9.3, which is compatible with RHEL but not based directly on RHEL’s code. Based on the RHEL code, we also have Rocky Linux 9.3 and Oracle Linux 9.3. SUSE is now offering support via its Liberty Linux program but is not yet offering its own Linux distribution. The OpenELA codebase is available, and presumably, Oracle, Rocky, SUSE and anyone else who wants to will use it as the foundation for their distributions.

Got all that?

For users, that means you have an embarrassment of choices for your RHEL-compatible Linux use. RHEL 9.3 and its variants are the latest and the first to appear since Red Hat’s recent code rule changes.

I’ve worked briefly on RHEL 9.3 with all the 9.3 variants, and, as far as I can tell, they’re all compatible with each other. They’re also all available on the major cloud providers.

So, which one is right for you?

If you need top-notch corporate support, RHEL is the Linux for you.

In addition, Red Hat has increasingly been incorporating other non-Linux features in its distros. For example, RHEL subscriptions now come with Red Hat Insights, a suite of hosted expert system services for developing and managing Linux platforms at scale. It also integrated Podman, its daemon-less tool for deploying, running, building and sharing Linux containers with pre-configured sets of Ansible DevOps roles and modules to streamline Podman system operations.

RHEL is also the foundation for essentially all of Red Hat’s other programs, such as its Red Hat OpenShift, its Kubernetes distribution, Red Hat OpenStack Platform and Red Hat Ceph Storage.

If your company lives and dies by Oracle, go ahead and stick with Oracle Linux. You can’t go wrong. If you’re using CloudLinux on your servers and it’s working well for you, there’s also no reason to switch.

You could use CentOS Stream for production, but I wouldn’t recommend it. Deploy CentOS Stream only if you need cutting-edge Linux features and have the in-house expertise to make the most of them. Otherwise, you’re just asking for trouble.

Finally, if you know your way around the old CentOS, either AlmaLinux or Rocky Linux are excellent choices. I use both on my servers and cloud instances, and I’ve been very happy with them.