AlmaLinux has dropped its aim to be 1:1 compatible with Red Hat Enterprise Linux (RHEL) and will instead target application binary interface (ABI) compatibility.
The move follows Oracle’s announcement of a way forward for its own distribution which, while critical of IBM and Red Hat’s decision to restrict access to RHEL source code, will also result in a loss of binary compatibility.
The company insisted that the decision would mean “very little change in [customers’] use of AlmaLinux”.
It also said that Red Hat-compatible applications would continue to run and the security updates would continue to flow.
However, by dropping the binary compatible aim it is difficult to see how a guarantee of all compatible applications continuing to run can be made, even with the ABI promise.
AlmaLinux also noted that users might also encounter bugs not in Red Hat, but not being bound to Red Hat’s release cycle means the distro can release fixes as expeditiously as it needs to.
What is application binary interface compatibility?
While 1:1 binary compatibility of the operating system is achieved through use of the source code - something Red Hat is discouraging through its restrictions - ABI refers to how an application works with the underlying operating environment.
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Red Hat defines ABI as “a set of runtime conventions that interact with a compiled binary representation of a program”.
Applications that are ABI-compatible should therefore continue to work on AlmaLinux. However, applications that are not - or make use of features outside of the ABI - might not function correctly.
It is also worth noting that at this point, ABI compatibility is presently an aim. As AlmaLinux says itself: “ABI compatibility in our case means working to ensure that applications built to run on RHEL - or RHEL clones - can run without issue on AlmaLinux”.
What does this mean for customers?
The fate of RHEL clones such as AlmaLinux has been in the balance since Red Hat’s decision to restrict access to the RHEL source.
Today’s announcement by AlmaLinux, and the earlier Oracle post, is an indicator that if a customer needs full RHEL binary compatibility, then a Red Hat subscription will likely be required.
Alternatives, such as Rocky Linux, still exist and intend to make use of UBI container images and leverage pay-per-use cloud instances in order to obtain the source and maintain 1:1 compatibility.
However, observers such as Matt Yonkovit, head of open source strategy at Scarf, told ITPro that Red Hat would likely find a way to close the loophole being exploited by Rocky Linux.
What has the reaction been?
The user community has mostly reacted positively to the news, mainly due to the removal of uncertainty over what AlmaLinux would do to deal with Red Hat’s decision. However, while there is empathy for AlmaLinux’s position, some users regarded the dropping of 1:1 compatibility as a “blow”.
“As much as I like Alma, the whole point of installing it for me was to be 1:1 with the RHEL I support at work. Warts and all.”
Another described AlmaLinux’s decision as “a very well thought out response to the changes”.
The furor surrounding Red Hat’s decision to restrict access to RHEL sources is set to continue despite the clarification given by AlmaLinux thanks to the differing approaches taken by distributions seeking to fill the space left by CentOS.
