Migration to Enterprise Linux Rebuilds – Rocky Linux & Alma Linux

The CentOS 7 end of life (EOL) date when the distribution stops receiving security patches is Jun 30, 2024. Prior to the acquisition of Red Hat by IBM in Dec 2019, Red Hat made available the source of Red Hat Enterprise Linux (RHEL) to, and financially supported the CentOS project in building a 1:1 compatible clone of RHEL with long-term update support for 10 years. As a downstream rebuild of RHEL, CentOS had always been bug-for-bug compatible with RHEL. It received patches for the same duration of time as its commercial counterpart. 

In Dec 2020, the IBM-owned Red Hat and the CentOS project announced that CentOS 8, the then-current version of CentOS, would not receive the full 10 years of update support from 2019-2029. Instead, the EOL life date for CentOS 8 was moved up to Dec 2021, giving users only one year to migrate to a supported OS. The CentOS project turned its efforts to CentOS Stream, a midstream distribution that is used to test code developed in the upstream Fedora Linux distribution before it filters downstream to RHEL’s commercial customers. 

CentOS 7, initially released in Jul 2014, remains supported until Jun 2024 — making it the last CentOS version to adhere to the 10 year release cycle. 

Migrating to Enterprise Linux Rebuilds before CentOS Goes EOL

The discontinuation of CentOS as a one-to-one compatible Enterprise Linux distribution to RHEL left the behemoth community scrambling to come up with alternatives before CentOS 7 and 8 would entirely lose support. Rocky Linux and Alma Linux were launched as fledging community-driven projects that would carry on the mantle of the original CentOS project as downstream rebuilds of RHEL — focused on stability and long term support. 

Rocky Linux

Founded by Gregory Kurtzer, CEO of CIQ and the Rocky Enterprise Software Foundation. Kurtzer was involved in leading the cAos Foundation in 2009, which rebuilt RHEL as cAos-EL, which would later be renamed CentOS and split off as the CentOS project.

Alma Linux


Governed by the AlmaLinux OS Foundation and supported by CloudLinux, Inc, a company that maintains the CloudLinux OS, a specialty Linux distro for hosting providers. As of Jul 2023, Alma Linux is a “friendly fork” of RHEL, rather than a 1:1 clone.

Both Rocky Linux and Alma Linux are available as machine images at all of the major cloud providers: AWS, Azure, and Google Cloud, and of course the ISOs can be deployed in an on-premise bare metal or virtualized environment as well. 

Rocky Linux vs. Alma Linux – 1:1 Clone or “Binary-Compatible”

In Jun 2023, Red Hat stunned the Enterprise Linux community another time by stating that it would cancel any RH subscription used to download the source code and errata of RHEL for creating EL rebuilds — a move of questionable legality under the GPL. In response to this, Alma Linux decided that it would remain binary-compatible with RHEL, but not necessarily be bug-for-bug compatible. On the other hand, the Rocky Linux project announced it would continue being a 1:1 clone of RHEL. It is conceivable that Rocky Linux can still get access to RHEL’s source code undetected by Red Hat, by taking out new subscriptions under different entities. 

What does this mean for IT departments using Enterprise Linux in their environment? Alma Linux can potentially experience bugs that are not in the equivalent RHEL version, but can also benefit from “out of cycle” patches contributed by the community, without waiting for the next RHEL release. It is, however, a fork of RHEL, so users may encounter cases where it behaves differently than RHEL.

As a 1:1 clone of RHEL, Rocky Linux is probably a better Enterprise Linux alternative where source code compatibility is required. This means that the bug fixes in a RHEL release will make it into the corresponding Rocky release — usually within a few days.

Is it better to convert or rebuild existing CentOS machines?

The migration path from non-Stream CentOS to a RHEL derivative depends whether you choose to convert your machines to a new distribution, or rebuild them entirely. Converting your machines to a new distro of choice may seem like the path of least resistance, but it involves the uncertainties of an OS version upgrade (in the case of moving from CentOS 7) combined with the possibility that certain repos or system services will not behave entirely the same under Rocky or Alma. 

Migration from CentOS 7 to RHEL rebuilds with ELevate Tool

Upgrading from CentOS 7 to 8 was never officially supported, so using a tool such as ELevate to migrate CentOS 7 to an 8.x version of Rocky or Alma Linux requires careful testing before proceeding with the approach in a production environment. After migrating a CentOS 7 system to the 8.x version of the RHEL rebuild of your choice, you can also optionally upgrade to 9.x of that distribution using ELevate. Rocky Linux and Alma Linux 8 have security support until May 2029, while release versions 9 have the same until Mar 2029, in line with the release cycles of RHEL 8 and RHEL 9 respectively.

Your team’s migration strategy from CentOS 7 to a RHEL rebuild will depend on your environment’s mission criticality and how long you will need to continue supporting the applications and services running in that environment. Converting CentOS 7 machines to a rebuild of RHEL 8 or 9 might require the least maintenance downtime if the packages running on them have a supported version for EL 8 or 9, preferably in the official repos. If your applications still have limited support for EL 9, it will be better to first upgrade to the 8.x version of a RHEL rebuild, then look at a subsequent upgrade to 9.x close to 2032 when the developers of those applications have updated them to better support EL 9. 

On the other hand, converting CentOS 7 machines to a rebuild of RHEL 8 or 9 and attempting to use it in production may be more risky to the business, if you don’t have the ability to test the upgrade in a “staging” environment first that is as similar to “production” as possible, and to “rollback” if the conversion and upgrade isn’t successful. It is easier to plan a move from CentOS to a compatible Enterprise Linux distro if your environment is already running on a virtualization platform (VMware, OpenStack) or cloud provider that supports snapshotting and cloning.

Rebuild a supported Enterprise Linux environment with Rocky or Alma Linux

Rebuilding the services running on your existing CentOS machines on fresh installs of Rocky or Alma Linux gives you the peace of mind of starting from a blank slate, without configs that might conflict with how the new distro handles things versus CentOS. Of course, this option requires inventorying your existing services & configs and rebuilding them on the new machine, so it is significantly more laborious. It does, however, result in systems that are more stable and “future proofed” for the years to come — as the individual components will also be updated to the latest stable versions.

As the deadline for upgrading from CentOS 7 to a supported distro is rapidly approaching, don’t delay in getting in touch with a technical consultant to plan your Enterprise Linux migration path. Continuing to use an unsupported distro may jeopardize the security of your systems and put your organization out of compliance with industry standards which require regular patching. Include as much information as possible, such as whether the machines to be migrated are on-prem or in the cloud, what services and applications they run, and which nodes require network connectivity to one another.