Hi Federico!
I'm a CERN employee currently evaluating Debian as a possible solution for our
systems in use to control particle accelerators. I would like to know more about
how the Debian community handles the Linux kernel integration. In particular, I
can't easily find the following information:
Cool, if you have more specific followup questions, don't hesitate to ask.
- Criteria to select a kernel version for a Debian release. It looks to me you
are following LTS releases, but as you know kernel LTS is a moving target in
terms of duration. So, how you choose?
Debian releases happen every two years at approximately the end of the second
quarter of uneven years. kernel.org LTS releases are usually announced/picked
by end of each calendar year and the latest kernel.org LTS gets picked as the
kernel version for Debian. Debian 9 has 4.9.x, Debian 10 had 4.19.x, Debian
11 and 5.10 and Debian 12 will have 6.1.
- How much a Debian kernel diverges from kernel.org release overtime?
Not much, you can have a look yourself for the current patches applied
to the 6.1.27 kernel which will be part of the initial Debian 12 release
(and future updates will rebase to 6.1.x LTS releases):
https://salsa.debian.org/kernel-team/linux/-/tree/sid/debian/patches
Anything in bugfix are cherrypicked bugfixes, debian/ contains a small
set of Debian-specific patches (for narrow toolchain or software freedom
issues) and feature contains a small set of backports (e.g. currently
for improved support for some non-x86 systems). In the past that also
included backported support for some NICs or RAID controllers (but these
usually only appear later in a release cycle).
- I see you explain how to build and run any kernel from kernel.org, but I do
not see and discouragement in doing so. Is this because you do not see any
known incompatibilities ?
Generally running a patched or bespoke kernel is supported. It's mostly
a matter of people power to do it properly (since one needs to rebase to
security updates and applying custom patches might need rebases if underlying
kernel code for updated).
Some parts of the OS (e.g. systemd) expectsa given set of kernel
features to be present to operate properly, but usually these are
quite common and unlikely to be absent in custom configs anyway.
If you start with the current Debian kernel config as a base (found
under /boot/config-VERSION) you won't run into any surprises.
Cheers,
Moritz