Ever get miffed reading about a major new Ubuntu release only to learn it doesn’t come with the newest Linux kernel?
Well, that’ll soon be a thing of the past.
Canonical’s announced a big shift in kernel selection process for future Ubuntu release, an “aggressive kernel version commitment policy” pivot that means it will ship the latest upstream kernel code in development at the time of a new Ubuntu release.
Future Ubuntu releases will ship the latest upstream kernel, even if only in ‘Release Candidate’ status
Yes, even if that upstream kernel hasn’t yet seen a formal stable release (and received the requisite newspaper-graphic-topped rundown on this blog).
Which is a huge change.
Currently, new Ubuntu releases include the most recent stable Linux kernel release at the time of the kernel freeze milestone in the Ubuntu development cycle.
Kernel freezes tend to be about 2 months before the final release, which can mean the kernel chosen for Ubuntu isn’t the latest at the time of release.
“This approach would guarantee stability on the appointed release day, but was proving unpopular with consumers looking to adopt the latest features and hardware support as well as silicon vendors looking […] to align their Ubuntu support,” Canonical’s Brett Grandbois explains.
But to “provide users with the absolute latest in features and hardware support, Ubuntu will now ship the absolute latest available version of the upstream Linux kernel at the specified Ubuntu release freeze date, even if upstream is still in Release Candidate (RC) status.“
For instance, Ubuntu 23.10 was shipped with Linux 6.5 upon its release on October 12. However, Linux 6.6 became stable on October 30. Ubuntu 23.04 launched with Linux 6.2, but Linux 6.3 was released less than a week later.
If the new selection policy had been in effect at that time, both releases would have included the newer versions.
Here’s a chart illustrating the new approach to kernel version selection Canonical’s engineers are intending to use future Ubuntu releases, starting with the upcoming Ubuntu 24.10 ‘Oracular Oriole’ release due in October (whose kernel freeze is next week):
As soon as the kernel does go stable, Canonical will package the changes and push it out as a software update. This change doesn’t mean Ubuntu users will be stuck running a RC build for the duration of the support cycle!
What if there’s a major last-minute issue that means that RC kernel doesn’t go stable for several more weeks after an Ubuntu release? Well, in that instance Canonical says “the die is cast” — it’ll have to deal with it.
A new Linux kernel typically emerges every 2-3 months based on a flexible schedule without strict deadlines. In the lead-up to the final release, about a month is devoted to issuing ‘release candidate’ (RC) builds. These continue until Linus Torvalds and his team deem the kernel stable, culminating in a formal announcement.
Conversely, Ubuntu adheres to a stringent release calendar that includes a definitive kernel freeze milestone. This approach ensures the kernel is thoroughly patched, integrated, and dependable not only for personal use but also for businesses, cloud operations, and other mission-critical applications.
This isn’t ‘new kernels, continuously’
This adaptation does not imply that Ubuntu is emulating System76’s strategy by rolling out new kernel updates continuously within its updates.
The supported kernel series at the time of launching, except for LTS versions’ HWE during point releases, is the sole kernel series maintained. An Ubuntu Linux kernel differs from a mainline kernel as it includes specific modifications and patches for supported technologies and OEMs by Canonical.
The suggestion to “Just package a new kernel and release it as an update” may seem simple but is impractical. This process would significantly increase the workload for Canonical, requiring them to package, test, and patch each new kernel while also providing ongoing support throughout the release duration.
However, users of Ubuntu 24.04 LTS will see advantages from this approach. HWE updates allow kernels from the interim releases to be available to LTS users. This means that newer kernel versions released during interim periods could be back-ported to them.
Win-win, right?