On 2020-09-10, The Natural Philosopher  wrote:
>
> Looking at my 'I only do one thing' Pi running 94 different processes,
> realistically how many of them do I need? And how could I get rid of them?
>
> I want to examine the pi as a reasonably real-time signal processing unit.
>
> I don't need disk access except to load the code. I may not need network
> access. I don't need logging. I sure don't need systemd. I don't need a
> gui.
>
> I just want to run one high priority daemon and one lower priority
> demon, with shared memory between them...is there something simpler than
> Linux? More like e.g. DOS?
>

You can start what you want. Linux is just the kernel. Alter the
cmdline.txt to tell the kernel what program to start (init=...), instead
of systemd or another init process.

see
https://unix.stackexchange.com/questions/428347/how-to-pass-arguments-to-a-linu
x-kernel-init-bootparam

Ok, your code that acts as init would have to start anything else you
wanted, or set up networking etc. but it can be done. I'm pretty sure
you could use busybox to form a minimal but adaptable boot environment.

This maybe of use...

https://pixelspark.nl/2019/making-your-own-linux-distribution-for-the-raspberry
-pi-for-fun-and-profit-part-2

All the parts are available from the standard Raspbian OS

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