AlmaLinux vs. Rocky Linux: Exploring the Key Differences

With the 2020 decision to discontinue CentOS Linux came two new Enterprise Linux distributions to fill the void: AlmaLinux, backed by CloudLinux; and Rocky Linux, driven by one of the creators of CentOS Linux, Gregory Kurtzer. Now with both boasting several successful releases, and both ready for use in enterprise deployments, comparing AlmaLinux vs. Rocky Linux is a worthwhile exercise for teams considering Enterprise Linux distributions in the post CentOS EOL era.

In this blog, I provide an in-depth comparison of AlmaLinux vs. Rocky Linux across all aspects of the two distros, including everything from community and sponsorship, to release lag and available enterprise support providers.

AlmaLinux vs. Rocky Linux

The main difference between AlmaLinux vs. Rocky Linux is their development process due to Red Hat's recent restrictions to RHEL source code. Rocky Linux still uses RHEL SRPMs for their upstream, whereas AlmaLinux's applications are built to run on RHEL and RHEL-based systems, but it is not an exact clone of RHEL. 

In June 2023, Red Hat announced that they would no longer publish the RHEL source code in favor of only releasing the CentOS Stream source code, which can be different than what is officially packaged in Red Hat Enterprise Linux.

This threw the RHEL-rebuild distros for a loop and Rocky Linux and AlmaLinux developed different solutions to this change.

Rocky Linux originally stated on their website that they are “designed to be 100% bug-for-bug compatible with Red Hat Enterprise Linux” and this has not changed as the original RHEL SRPMs continue to be used as the upstream for Rocky Linux.

AlmaLinux took a different approach, though, and the claim on its website that AlmaLinux is “1:1 binary compatible with RHEL and pre-Stream CentOS” has been replaced with “AlmaLinux OS is binary compatible with RHEL” which allows AlmaLinux to run applications built to run on RHEL and RHEL-based systems, but relieves them of publishing an exact clone of RHEL.  

Watch this brief video featuring Greg Kurtzer (founder of Rocky Linux) and benny Vasquez (Board of Directors Chair for the AlmaLinux OS Foundation) explaining their respective projects' missions and goals.

Community and Sponsorship

The Rocky Enterprise Software Foundation (RESF) is a Public Benefit Corporation created by CentOS Linux co-founder Gregory Kurtzer “to organize a community around enterprise, research, academia, individuals, and other institutions” specifically for Rocky Linux. The RESF is made up of team leads and other trusted individuals from within the Rocky Linux community for the purpose of transparency and mitigating the possibility of an individual or external entity taking control of the project.

RESF invites sponsors and partners to contribute to Rocky Linux with a current balance of 12 sponsors, 12 partners, and 2 support providers as listed on the Rocky Linux website. Gregory Kurtzer’s CIQ is the founding sponsor, the founding partner, and a support partner for Rocky Linux.

AlmaLinux is provided by the AlmaLinux OS Foundation, a 501(c)(6) non-profit established to “(i) further develop and maintain AlmaLinux OS as a no registration, ad free, stable, open source Linux distribution for the benefit of and free use by the general public, (ii) facilitate and promote the growth of a community of vendors and partners delivering solutions based on or complimentary to AlmaLinux OS, and (iii) undertake such other activities which its Board of Directors may from time to time approve.” The Foundation consists of Contributor Members, Mirror Members, Sponsor Members, and Alumnus Members.

The AlmaLinux website presently lists 21 backers and 1 commercial support vendor.

CloudLinux is AlmaLinux’s founding company, providing $1 million in sponsorship annually.

Editor's Note: OpenLogic is a sponsor of both the RESF and the AlmaLinux OS Foundation, and is a technical support vendor for Rocky Linux and AlmaLinux.

Popularity / Adoption

None of the following numbers are indicative of a clear winner by themselves. As mentioned above, there are different reasons why one distribution or another may be the best for a particular deployment. For more data on enterprise Linux distributions and their usage, check out the most recent State of Open Source Report. 

Distrowatch

Looking at the trending data for the last 12 months shows a good trendline for popularity for the distributions (based on page hits on distrowatch.com).

When this article was originally published, the popularity looked like this:

• 12 months ago, CentOS was ranked 29th, with AlmaLinux and Rocky Linux following at 31st and 35th respectively.
• 6 months ago, AlmaLinux had climbed above CentOS into the 25th spot, with Rocky at 32 and CentOS at 33.
• 3 months ago, AlmaLinux peaked at 16, with Rocky Linux at 22 and CentOS dropping to 37.
• Last month, Rocky Linux rose to spot 15, with AlmaLinux dropping to 34, and CentOS falling further to 40.

Now, the popularity looks like this:

• 12 months ago, CentOS was ranked 50th, with AlmaLinux and Rocky Linux following at 18th and 43rd respectively.
• 6 months ago, AlmaLinux dropped into the 24th spot but still besting Rocky at 42 and CentOS at 54.
• 3 months ago, AlmaLinux continued to drop to 37 with Rocky Linux at 63 and CentOS dropping to 59.
• Last month, Rocky Linux pretty much maintained its rank at 62, with AlmaLinux continuing to drop to 54, and CentOS falling further to 65.
   

Cloud Provider Marketplace Images

Let’s look at the three largest cloud providers: AWS, Azure, and Google Cloud. All three cloud providers have official and 3rd party images available for both AlmaLinux and Rocky Linux.

AWS

On AWS, AlmaLinux and Rocky Linux both have official offers for AlmaLinux 8 and 9 for x86_64 and arm64. There are approximately 565 total AlmaLinux offers and 668 total Rocky Linux offers, mostly from 3rd party publishers.

Azure

On Azure, AlmaLinux has official offers for AlmaLinux 8 and 9 (both x86_64 and arm64) as well as an offer for AlmaLinux 8 HPC (x86_64). Rocky Linux has official images for Rocky Linux 8 and 9 (both x86_64) on Azure. When this article was first published, there were a total of 28 AlmaLinux offers and 27 total Rocky Linux offers, but now there are many, many offers for both (Azure’s marketplace search doesn’t restrict to the search term, thus non-Rocky and non-Alma results are returned so getting an accurate number is difficult).

Google Cloud

Google Cloud lists an official AlmaLinux 8 and 9 product, nine 3rd party AlmaLinux products, an official Rocky Linux 8 and 9 product, and eleven 3rd party products.

On-Premise Images

AlmaLinux and Rocky Linux offer on-premise images in their repositories.

AlmaLinux offers a multitude of GenericCloud, GenericCloud-UEFI, and OpenNebula images for AlmaLinux 8 and 9 for x86_64, aarch64, s390x, and ppc64le.

Rocky Linux offers an even wider variety of Azure, Container, EC2, OCP, and GenericCloud images for Rocky Linux 8 and 9 for x86_64, aarch64, s390x, and ppc64le.

Hashicorp’s Vagrant Cloud has listings for both distros, too.

Searching for “AlmaLinux” returns twelve pages of results with the official AlmaLinux 8 and 9 boxes supporting hyperv, libvirt, parallels, virtualbox, and vmware_desktop with a combined download count that exceeds 54,000.

A search for “RockyLinux” also returns twelve pages of results with the official Rocky Linux 8 and 9 boxes supporting libvirt, virtualbox, and vmware_desktop with a combined download count around 29,000.

Outside of the official releases, 3rd party box publishers make up the majority of the available boxes, including popular box publishers like bento, boxomatic, and OpenLogic.

In addition to on-premises vagrant boxes for virtualbox and vmware_desktop, OpenLogic also publishes boxes which allow vagrant to manage cloud-based virtual machines on AWS, Azure, and Google. Hashicorp doesn’t provide granular, per-environment usage counts, but they do provide a total download count. OpenLogic’s Rocky Linux 9 image continues to be marginally more popular than our AlmaLinux 9 image, and our Rocky Linux 8 image is about twice as popular as our AlmaLinux 8 image.

Torrent Seeds

The torrent numbers are based on the official torrent files published in the respective distributions’ mirrors. Since x86 is the most popular architecture for AlmaLinux and Rocky Linux, I’ll focus on the number of seeds for only the x86-64 torrents. (Numbers are as of Oct 20, 2023.)

AlmaLinux’s torrent file contains all three ISO variants (boot, minimal, and DVD), whereas Rocky provides torrents for each of their ISO variants. Rocky’s dvd1 torrent is the most popular regardless of version, so I’ll use that Rocky torrent for the comparison.

AlmaLinux has a total of 471 seeds (an average of 67 seeds per torrent):

Rocky Linux has a total of 786 seeds (an average of 112 seeds per torrent):

Looking at EL8.8 and EL9.2, AlmaLinux has 81 and 176 seeds, while Rocky has 115 and 308 seeds, respectively.

The number of seeds doesn’t necessarily tell the whole story, since many torrent clients are only active while the end user downloads the necessary files.

So, let’s look at the sharing ratio of my personal torrent client. I add the official torrent files to my personal torrent client as soon as possible after they are released to the public, typically within an hour or so of publication, and always within 24 hours.

My sharing ratio for AlmaLinux is:

My sharing ratio for Rocky Linux is:

As we’ll see below in the Release Lag section, AlmaLinux has a track record of beating Rocky Linux to GA release, but Rocky Linux appears to be downloaded (via torrent) more than AlmaLinux in all cases.

Docker Images

The official docker images for Rocky Linux exceeds 10 million downloads whereas AlmaLinux downloads are listed at over 1 million. By pulls alone, Rocky Linux is leading AlmaLinux by a factor of about 2.5.

Development Process

Rocky Linux and AlmaLinux both have minor differences in how they develop their distributions, including differences in build systems and architecture support.

Upstream

AlmaLinux and Rocky Linux both utilize source code from Red Hat as their upstream, but each goes about it a little differently.

AlmaLinux’s goal of now being “RHEL binary/ABI compatible” offers more flexibility on where source code comes from since duplicating RHEL exactly is no longer paramount. I was unable to find record of exactly where the source code/patches are now pulled from, but an article published by AlmaLinux states they are using “several sources.”

Rocky Linux utilizes at least two methods of obtaining the RHEL source code in order to continue to strive to be “100% bug-for-bug compatible.” One method is using RHEL UBI (Universal Base Image) containers and the other is launching pay-per-use cloud instances, both of which provide legitimate access to the Red Hat source.  

These changes have all been after RHEL 8.8 and 9.2 were released so we haven’t yet seen what will happen when the next minor version (or major version, for that matter) of RHEL is released. Chances are that we will see variations in expected release lag (see below) but that’s purely conjecture.

Build Systems

AlmaLinux and Rocky Linux are both built using their own build systems.

AlmaLinux utilizes a custom AlmaLinux Build System (ALBS) to produce their assets. I couldn’t find any hard information about when AlmaLinux started to use this build system, or if they were using it from the start, but the first build on build.almalinux.com is from Sept 15, 2021, so I think I can safely assume that AlmaLinux 8.6 and 9.0 were built with ALBS, but earlier releases may have been also.

Prior to Rocky Linux 9.0, the Rocky Release Engineering team used Koji (and other Fedora components) to build Rocky Linux. Starting with Rocky Linux 9.0, the build system has been replaced with Rocky’s own Peridot. It was the change of build system which induced a lot of the release lag for RL 9.0, which we’ll talk about in a bit.

Architecture Support

x86_64 support was the first platform that both distros released, and both now support aarch64, ppc64le, s390x, and x86_64 with their 9.0 releases.

Starting with AlmaLinux 8.4, aarch64 support was added, AL 8.5 added ppc64le, AL 8.6 offered s390x support, and AL 9.0 introduced s390x support.

In contrast, Rocky Linux included support for aarch64 from the start, but didn’t include support for ppc64le or s390x until RL 9.0.

Release Lag

There are two types of release lag that I like to keep an eye on, initial release lag and update release lag.

Initial Release Lag

The first is initial release lag. Typically, this applies to major releases, but since both AlmaLinux and Rocky Linux joined the RHEL rebuild party mid-EL8.x, it also applies to minor releases.

AlmaLinux was the first of the RHEL rebuilds to receive a GA release with AlmaLinux 8.3 published on Mar 26, 2021.

As mentioned earlier, the entire Rocky Linux build system was swapped out for RL 9.0, which explains the higher release lag for RL 9.0. Now that Peridot is in production, it will be used to build all future Rocky Linux releases.

Regardless, for the last two minor releases, both AlmaLinux and Rocky Linux have had minimal wait times after RHEL was published.

Update Release Lag

The second type of release lag is update release lag. This is the lag between when Red Hat publishes a package update and when the RHEL rebuild distribution releases their package update.

With so many updates to consider, I’m going to look at just a couple of the kernel updates to get a sample of expected release lag. The timestamps I am using for comparison are the file dates on my local mirror.

As we can see, from the 8.4 to the 8.7 releases, the update release lag was minimal for both distributions, with a typical lag of a day or less after Red Hat publishes the update for RHEL. There has been a little more variability in the release lag starting with the 8.8 release and with some of the 9.x releases, but the lag is still generally less than we’ve seen with CentOS Linux 7.  

Feature Inclusion

The features included with both distributions should be the same. Looking at the repos that each distribution offers, the same basic repositories are present.

Where they differ is that Rocky Linux provides a ‘devel’ repo which contains packages that are required for building other packages.

Otherwise, the package offerings for both AlmaLinux 8.8 and Rocky Linux 8.8 are nearly identical with both repos containing around 6850 RPMs. The same is seen with AL 9.2 and RL 9.2 with approximately 5880 RPMs published by both. Most of the changes are optional packages built from the same specfile or distro-specific packages.

Both AlmaLinux and Rocky Linux provide migration tooling to assist with system conversion from another distribution.

Get Migration Guidance and Support

Upgrading/migrating between major versions (7->8, 8->9, etc.) is complicated, and not something to be entered into on a whim. Migration between distributions within a major version (RHEL8->Rocky8, Oracle8->Alma8, etc.), though, is fairly well documented and has a history of great success. If you are considering migrating between versions, OpenLogic can provide assistance with determining the best practices to use and can even tool custom procedures to help ensure successful migration of your mission critical systems.

Explore OpenLogic Migration Services

AlmaLinux provides the ELevate tool which supports “migration between major versions of RHEL derivatives" so that users can "easily go from CentOS 7.x to any 8.x”.

Rocky Linux provides the migrate2rocky tool. Rocky’s utility is intended to migrate within a major version, providing different scripts for EL8 to Rocky8 or EL9 to Rocky9 migrations. migrate2rocky minimizes the number of variables it needs to handle during migration by requiring the EL8.x system to be upgraded to at least 8.5. The documentation includes commands to modify the CentOS repos so CentOS systems < 8.5 can upgrade 8.5 prior to migration.

Support and Enterprise Viability

Enterprise viability is strong with both options. Here at OpenLogic, we look at several factors to determine if a distribution is “enterprise ready.” The items that the distribution must provide are:

• A rich package count, including a widely distributed mirror network
• Updates (major and/or minor version OS releases)
• Patching (package updates within a major/minor version)
• Documentation

There are two other items that are necessary. These may not be provided by the distribution themselves but may be provided by one or more 3rd parties:

• Support with an SLA
• Availability of professional services

AlmaLinux and Rocky Linux both provide all the distribution items as well as support from their founding companies.

Checking the last box of this Enterprise Linux checklist, professional services may be available from the founding companies, but 3rd party support and professional services are available. For instance, OpenLogic provides support and professional services for AlmaLinux, Rocky Linux, and several other Enterprise Linux distributions.

Other Notable Differences

Some Linux distributions have been considered not ready for enterprise use simply due to the lack of public mirrors hosting the distro’s packages. If a distribution only has a very small handful of mirrors, the possibility of mirrors being unreachable (or unusably slow) is too high for mission critical systems to rely on them.

Neither AlmaLinux nor Rocky Linux need worry here!

AlmaLinux presently has 302 mirrors announcing support for FTP, HTTP/HTTPS, and RSYNC while Rocky Linux presently has 165 mirrors announcing support for HTTP/HTTPS and RSYNC.

Final Thoughts

While comparing AlmaLinux vs. Rocky Linux it is a worthwhile exercise for teams considering their next Enterprise Linux distro, at the end of the day both distros are very similar. And, given the quality of releases to this point, enterprises can find success with either option.

Need Support for AlmaLinux or Rocky Linux?

OpenLogic offers expert, 24/7/365 support for AlmaLinux, Rocky Linux, and other top open source Enterprise Linux distributions. Learn more about what we offer via the links below.

Talk to a Linux Expert  Download Enterprise Linux Support Datasheet

Additional Resources

• Video - How Rocky Linux and AlmaLinux Keep Their Distributions Secure
• White Paper - Decision Maker's Guide to Enterprise Linux
• Webinar - Exploring the Post-CentOS Landscape with AlmaLinux and Rocky Linux
• Blog - CentOS Stream 10 Preview
• Blog - Long-Term Outlook for CentOS 7 Support
• Blog - State of Open Source Report: Top Enterprise Linux Distributions
• Blog - How to Plan a CentOS to AlmaLinux Migration
• Blog - Planning a CentOS to Rocky Linux Migration
• Blog - All About Rocky Linux 9.1
• Blog - What's New in AlmaLinux 9
• Blog - Finding the Best Linux Distro

Editor's Note: This blog was originally published on August 9, 2022 and was substantially updated on October 26, 2023 and then again on November 17, 2023 after the release of 9.3.