Rocky Linux release attracts 80,000 downloads as ex-CentOS users mull choices

Who has the best RHEL clone? Rivals jostle for position

Rocky Linux 8.4, which was made generally available early last week, attracted 80,000 downloads within 72 hours, but disaffected CentOS users are wondering whether Rocky, rival AlmaLinux, or some other OS, is the right next move.

Both Rocky Linux and AlmaLinux are designed to be binary-compatible with Red Hat Enterprise Linux (RHEL), while also being free software, for those who can manage without Red Hat's support. Red Hat's CentOS used to fulfil this role, until the company declared that in future it would be only CentOS Stream that previews rather than follows what will be in RHEL.

AlmaLinux, sponsored by CloudLinux, was first out of the gate with a stable release at the end of March. Rocky Linux, a project led by CentOS co-founder Greg Kurtzer, took a little longer to reach general availability, perhaps because it was built from scratch, whereas the CentOS-based CloudLinux OS already existed.

Another factor in the delay, according to the Rocky Linux FAQ, was the effort put into governance. "If our only goal for Rocky Linux was to debrand and repackage RHEL, we would have been done much sooner. However, what we had to do differently is figure out how we could keep Rocky Linux in the hands of the community. Carefully devising this strategy ensures that Rocky Linux will never meet the same fate of CentOS," it says.

The solution it came up with was to create the Rocky Enterprise Software Foundation (RESF) with a "community charter". According to the FAQ, "Rocky Linux will never be controlled, purchased, or otherwise influenced by a single entity or organization."

The AlmaLinux project came up with what seems a similar solution, creating the AlmaLinux Foundation, with board members including Igor Seletskiy, CEO of CloudLinux, Jesse Acklund from cPanel, and open source advocate Simon Phipps.

Despite appearing a little later, the Rocky Linux project has momentum. It reported that "within 72 hours of launch, Rocky's assets have been downloaded nearly 70,000 times from our Tier0 mirror, served from Fastly – not counting the number of downloads from our mirrors, of which we have nearly 100 – and we count approximately 10,000 downloads of our torrent file." We note, though, that because of the mirrors it is not possible to get an accurate total count. Another indication of support is that Google has made a customised Rocky Linux for installation on Google Compute Engine (GCE), and is now a "Principal Sponsor" of RESF. AlmaLinux is also available on GCE but as a "community supported image" which means it is "not directly supported by Compute Engine." Microsoft has "signed on as a partner of RESF" and will ensure Rocky Linux availability on Azure.

AlmaLinux has also been well received with mostly positive reviews from early adopters. This week the project released 8.4 stable for ARM64, assisted by Arm and tested by AWS on its ARM-based Graviton VM instances (Rocky also has an ARM build available). Similarly, it is impossible to be precise about the number of AlmaLinux downloads but a recent press statement spoke of "tens of thousands of downloads from its primary mirror site, plus an undetermined number from 133 other mirror sites around the world."

It's quite hard to pick a clear technical reason to pick one over the other... you now have two distributions continuing where there was one before but both rely on a parent who owes them nothing

That said, AlmaLinux does not seem to have attracted as big a community around it. The AlmaLinux chat server has 203 member in its general channel at the time of writing, versus Rocky Linux with 5,536 (both run on Mattermost servers). There is a sense that these two distributions are jostling for position. A comment (registration required) on the AlmaLinux chat server says what many must be thinking: "What do I do for CentOS now: as a relative outsider, it's quite hard to pick a clear technical reason to pick one over the other... you now have two distributions continuing where there was one before but both rely on a parent who owes them nothing. And the 'community' that was there, such as it was, is now fractured. Hard to tell who will still be here five years from now."

Perhaps conscious that adoption decisions made today may stick for a long time, the projects are advertising. "We are about to start AlmaLinux ads – all sponsored by money from CloudLinux at this point," said (registration required) Seletskiy. Asked why a FOSS project needs ads, he said: "If there are no user adoptions, commercial vendors will not support it, and then all the cool shit we would do – just wouldn't matter." Ads for Rocky Linux have also been appearing, from Ctrl IQ, a company of which Kurtzer is CEO, that calls itself "the official founding support and services partner for Rocky Linux," though it also specialises in HPC (high-performance computing).

Some apparent AlmaLinux fans are taking other approaches, like the user "Rabiton" who turned up on Reddit to question whether Rocky Linux is as community-spirited as it appears, claiming that "Rocky is for profit company... nothing prevents Greg from selling it when he decides he has enough." He also self-identified as "a sock puppet and I don't like community being taken for a ride."

Is Rocky Linux vulnerable to this accusation? Whereas the AlmaLinux OS Foundation is a 501(c)(6) non-profit entity, the RESF is a Public Benefits Corporation, which is a for-profit company though one obliged to focus on a positive social impact rather than just the interests of its shareholders.

Kurtzer said this is not at odds with commitment to the community. "I own the RESF because I've gone down the shared ownership 501(c) path before with the Caos Foundation (the org that hosted CentOS) and within a couple of years, CentOS was manipulated out of the non-profit," he said.

"I've seen other 501(c) entities created within the open source realm, some of them having better results than others. What I've learned was that simply being a non-profit is not a magic pill for honesty and integrity. So we decided to go with a PBC (Public Benefits Corporation) and be very clear that we are not motivated by profit, but rather public benefit."

He added: "Do I have to be the sole owner of the RESF? No, and at some point we will revisit this, as well as becoming a non-profit. How long did Linus Torvalds control and 'own' Linux? Did that stop you and others from using it? No."

The corporate structure matters less in open source than anywhere else because you can lift and shift, the ability to fork

In order to succeed long term, open-source projects need to have both sufficient community around them and an appropriate level of sponsorship and financial support; there are many routes to this goal and no single best way to achieve it. Amanda Brock, CEO of Open UK, an open source advocacy group, said: "In open source, the thought process is that the community has control because they can lift the code and fork... the corporate structure matters less in open source than anywhere else because you can lift and shift, the ability to fork."

This is the exact path that has now given rise to both Rocky Linux and AlmaLinux. When CentOS went along a path that many of its community disliked, the open-source licensing of RHEL enabled these other projects to form and succeed. Technically, these distributions are very alike and switching between them is easy, since both are binary compatible with RHEL.

As one Rocky user said on Reddit, in response to the idea that Rocky Linux could be acquired: "Maybe it will and I'll switch to the next fork. If it does live as long as CentOS, I'll have about 20 years." ®