Google has announced it will continue to support the Linux kernels it uses in Android for four years following changes to how LTS Linux kernels are supported.

In late 2023, Linux kernel developer Jonathan Corbet announced that support for long-term support (LTS) kernels would drop from six years to just two. LTS kernels form the basis of some of the most popular Linux distros, such as Debian and Ubuntu. LTS kernels have security and bug fixes backported throughout the life of the kernel, allowing distros to provide long-term stability and reliability while still having the latest security and bug fixes.

“There’s really no point to maintaining it for that long because people are not using them,” Corbet said at the time.

“Maintainers are burning out [because] maintainers don’t scale,” added Josef Bacik, kernel file system developer and kernel maintainer.

“This cannot stand,” added Darrick Wong, a senior kernel maintainer. “We need help.”

Google uses LTS Linux kernels as the backbone of Android, benefiting from the security and bug fixes those kernels provide to help protect Android users. The company describes its kernel strategy for Android common kernels (ACKs):

When a new LTS is declared upstream, the corresponding common kernel is branched from android-mainline. This allows partners to begin a project prior to the declaration of the LTS version, by merging from android-mainline. After the new common kernel branch is created, partners can seamlessly change the merge source to the new branch.

Other common kernel branches receive regular merges from their associated LTS kernel. These merges are normally done immediately after the LTS release is posted. For example, when Linux 6.1.75 was posted, it was merged into the 6.1 common kernel (android14-6.1). Partners are strongly encouraged to update their kernels to stay up-to-date with LTS and Android-specific bug fixes.

Needless to say, the changes to the Linux kernel LTS period directly impact Google’s efforts, limiting the viable kernels that can be used for Android:

Before Android 15 (AOSP experimental), any of the three most recent kernels could be used for device launch. Starting with Android 15 (AOSP experimental), the two most recent kernel versions can be used for device launch. The launch kernels for Android 15 (AOSP experimental) are android15-6.6 and android14-6.1.

Because of these changes, Google says it will now provide four years of support for the LTS kernels it uses as the basis of Android, going above and beyond the initial two.

ACKs might be supported for longer than the corresponding upstream stable kernel at kernel.org. In this case, Google provides extended support until the end-of-life (EOL) date shown in this section. When kernels are EOLed, they are no longer supported by Google and devices running them are considered to be vulnerable.

Beginning with kernel 6.6, the support lifetime for the stable kernels is 4 years.

The company provides the following table to show how long each specific kernel will be supported:

Google’s announcement should be welcome news for Android developers and vendors.