The new Rocky Linux 9 is one of the unofficial successors to the discontinued CentOS. That originally functioned as a clone of Red Hat Enterprise Linux (RHEL), which could be used without a license but also came without support. However, Red Hat scrapped the distribution as part of the development of RHEL 9 and instead made CentOS Stream the upstream distribution of future RHEL versions, much to the dismay of many users. Theoretically, administrators with existing systems based on CentOS would have been left out in the rain if several self-proclaimed successors had not quickly been founded within the community.
From a technical point of view, everything can be quickly said about Rocky Linux 9, because the distribution is bug-compatible with RHEL 9 and inherits all of its changes: Linux 5.14, which is no longer entirely fresh, with a number of additional patches is also part of the package, as is a fresh runtime environment for containers, an improved one SELinux and the ubiquitous NetworkManager, which finally replaces the old network scripts. On top of that, there is a bunch of reasonably up-to-date software that Red Hat – and therefore also Rocky Linux – probably intends to update via containers in the future.
If you are running existing CentOS 8 systems, you should first convert them to Rocky Linux 8 using a script provided by the project, in order to then import the update to Release 9 – the manufacturer officially supports such an update, as with RHEL 9 .
Innovations mainly in the background
Almost more spectacular than the changes in Rocky Linux itself, for which the provider naturally has little leeway, are the changes to its own infrastructure, which Rocky Linux released at the same time as the new release. The project is comparatively late with its RHEL 9 clone, as the competition at AlmaLinux presented their version 9 of an RHEL clone more than a month ago. According to the developers, however, there are tangible reasons for this: In the background, an automatic build framework was built in order to (partially) automate new versions of Rocky Linux in the future and thus bring them to the public much faster.
Technically, this makes perfect sense: As with CentOS, the main differences in Rocky Linux compared to the original are in terms of graphics, the Red Hat logo used, or central components such as Red Hat’s manager for subscriptions. However, building new binary packages with different graphics from the RPM sources—all of which Red Hat provides—is a task that can be automated just as easily as removing individual packages from the target distribution’s package list. A small number of packages remain that the developers actually have to get involved with for various reasons, so that the waiting time between a RHEL and a Rocky Linux release is reduced to a few weeks if possible.
According to their own statements, the developers have already successfully used parts of the automated infrastructure in Rocky Linux 9, so that they are prepared for the future. Only Rocky Linux 9.1 will probably show whether the self-constructed framework really keeps what the developers expect from it. Rocky Linux 9 is now available for download as a free ISO image. With Google, one of the major cloud providers is now also relying on Rocky Linux as the CentOS successor.