The kernel

SakuraOS builds the CachyOS kernel, which is the scheduler work that makes an Arch desktop feel quick. Machines whose processors cannot run it get the standard Arch kernel instead, automatically, with nothing to choose and nothing to undo.

What the tuned kernel is

It is built from the CachyOS sources, pinned to a specific commit and verified against the upstream signing keys rather than tracking a moving branch. The variant is the BORE scheduler with sched-ext support.

We build it rather than repackaging theirs, so the same repository signature covers it as everything else on the system. The work is theirs; the build is ours.

The processor check

The tuned kernel is compiled for x86-64-v3, roughly meaning AVX2, which arrived on Intel with Haswell in 2013 and on AMD with Excavator. A processor older than that cannot execute the binary at all.

So the installer asks the one component that already knows the answer: the dynamic loader.

/lib/ld-linux-x86-64.so.2 --help | grep "x86-64-v3 (supported"

glibc's loader lists the microarchitecture levels it will load libraries for, and it is right about the machine it is running on by definition. That beats parsing CPU flags out of /proc/cpuinfo and guessing which set constitutes v3.

If the loader answers and does not list v3, that is a real answer and the standard kernel is installed. If the loader cannot be asked at all, the standard kernel is installed too, because the safe direction is obvious: a kernel that runs everywhere on a fast machine costs some performance, and a kernel that cannot execute on an old one costs the whole machine.

Why it is built GENERIC_V3

The upstream build defaults to optimising for the processor doing the building, which is right for somebody compiling their own kernel and wrong for a distribution. Left alone it would produce a kernel tuned for our build server and no one else's computer.

We set the target explicitly to a generic v3 build, so every machine that supports v3 gets the same binary and the same benefit.

What older machines get

Stock Arch linux. Every other part of SakuraOS is identical: same desktop, same store, same restore points, same recovery. There is one image to download, and a first-generation i7 installs the same one a Ryzen 9000 does.

Most distributions that chase performance quietly stop supporting older hardware. This is the alternative to that, and it costs one check at install time.

Keeping the boot image honest

The kernel lives in a unified kernel image on the EFI system partition while its modules live in the root subvolume, and the two can disagree after a rollback across a kernel update. A service checks that on every boot and repairs it. See Recovery.