Custom kernel for RPi2 and 3

[George Rosamond]

bob prohaska:
> On Wed, Feb 21, 2018 at 02:18:21AM +0000, tech-lists wrote:
>> On 20/02/2018 16:19, bob prohaska wrote:
>>> Does anyone have a recipe for building a custom RPi2 or RPi3 kernel?
>>
>> for rpi2 I comment out /remove what I don't need [0]. On rpi3 if I'll
>> use GENERIC-NODEBUG, or comment out what's not needed. But
>> GENERIC-NODEBUG is good and still has *some* ability to debug. I get a
>> smaller system by adding WITHOUT= statements to various bits that will
>> never be used in the context. man 5 src.conf
>>
> 
> It's not trivial to figure out which of those "WITHOUTs" apply to the Pi2
> or Pi3. I was hoping for a pointer to a list or perhaps a more restrictive
> starting point. Still, it _is_ a starting point, thank you!
> 
> How much did the resulting kernel shrink? Seems to me I only shaved
> less than 1 meg (~11 meg became ~10meg) by tampering with GENERIC.
> It didn't seem worth the effort if that's all that can be accomplished. 
> My hope was to trim it by maybe half...  Perhaps that's fantasy...  
> 
> One sidelight was all the kernel modules that get compiled. It would
> be nice, if not necessary, to omit compiling those that aren't needed.
> 
> 
>>> I tried it, by simply commenting out drivers I didn't recognize in
>>> GENERIC, but after much trial-by-error the kernel didn't shrink a lot.
>>> Having since learned that GENERIC is the tail of a much larger beast,
>>> perhaps there's a more intelligent method.
>>>
>>
>> Are you compiling on the pi? I don't because it's painfully slow and bad
>> for the microsd. I cross-compile on a faster machine using
>> https://github.com/freebsd/crochet - basically do this every time
>> there's a problem/vulnerability that can't be patched and building world
>> is needed.
>>
> Yes, compiling on the Pi. That way the test machines will start having
> flash problems before the "production" machines and I'll have time to
> replace storage media before there's a data loss.
> 
> Thanks very much!

Bob:

This script can generate an /etc/src.conf based on the running system,
extracted from /etc/src.conf(5). Since there's no standard /etc/src.conf
through FreeBSD versions, it's a hassle to maintain without it.

http://wiki.torbsd.org/doku.php?id=en:a_shell_script_to_convert_src.conf_5_contents_to_an_example_etc_src.conf_file

HTH

g