Linux 6.12 is the new long term supported kernel

Last month’s new version of the Linux kernel, 6.12, has been confirmed as the newest LTS release… which also marks the end of the line for kernel 4.19.

Kernel version 6.12 was released on November 17, and at the end of last week, without any fanfare, it also became the latest long term supported version – as confirmed by Phoronix.

Linux kernel 6.12 is an interesting release. Perhaps the biggest change is that This version finally sees the completion of the process of incorporating the patches to make the kernel capable of real-time operation. Labelled PREEMPT_RT, these started development 20 years ago, and for a couple of years they’ve been used in the special Ubuntu Real-time edition.

The previous step in taking them mainstream was merging the locking code, which went in to kernel 5.15 in 2021.) This latest merge makes it possible to enable both hard and soft real-time behaviour in the kernel.

Building on functionality that we described going into kernel 6.11, if kernel 6.12 panics, it can display the crash message as a QR code, which will make debugging easier. It also introduces a new class of process scheduler, the Extensible Scheduler, which allowes eBPF programs to define CPU scheduling; LWN did a deep dive on how this works last year.

Along with this are all the usual bug-fixes and assorted improvements to hardware support, filesystems, power management, and so forth, as seen in every new kernel release.

One in, two out
As we reported last year, the overworked kernel maintainers have been compelled to reduce the number and lifetime of LTS kernel versions. As such, the lifetime for 6.12 is currently listed as being until December 2026. The counterpoint to a new member of the list of LTS kernels, though, is that others fall off the end.

At the same time as 6.12 became the latest LTS kernel, Greg Kroah-Hartman announced the last bugfix release of kernel 4.19: version 4.19.325. He notes that, even after 325 versions, there are a lot of outstanding known bugs in this version:

As such, this is the final release, meaning that this is now an unsupported kernel:

The end of official support for kernel 4.19 coincides with the end of third-party extended support for kernel 4.14. Back in March, we reported on an unexpected extension of life support for that release, but it too is due to fall off its perch at the end of this year.

This marks the end of the line for all versions of kernel 4.x. It’s been around for nearly a decade: kernel 4.0, codenamed Hurr durr I’ma sheep [sic], was released on 12 April 2015. (Those were manifestly less serious times in Linuxvania.)

Long-term support for Linux kernels is about to get a lot shorter

Linux kernel 4.14 gets a life extension, thanks to OpenELA

Ubuntu LTS kernels will get one decade of fixes … still

Long-term supported distros’ kernel policies are all wrong

Of course, some specific versions in various downstream vendors’ products will be supported for longer. Each distro vendor with fixed release cycles picks its own kernel versions for each product release, which means that individual vendors keep supporting their own specific kernels long after the upstream versions wither on the vine. Long-term support versions of Ubuntu get a decade of kernel fixes. Red Hat does similar, for even older kernels.

There is room for a great deal of improvement here. The Linux industry is a mature, international multi-billion dollar business now. We feel it’s time for stable distro vendors to work out ways to synchronize their long-term release cycles with the kernel team’s long-term release cycles. Some distro vendors are on board, but not the big players. It is already past time this happened. ®