On a sunny day (Sun, 1 Mar 2020 03:28:59 +0000 (UTC)) it happened bob prohaska
 wrote in :

>This is probably a dumb question, but I'll ask anyway:
>
>Is it possible to download source code for the kernel and user
>software and rebuild the command line part of raspbian on the Pi?
>
>I understand it's not done that way, I'm merely curious.
>
>Thanks for reading,
>
>bob prohaska

Yes why not, google finds this for the kernel:
 https://github.com/raspberrypi/linux
have not tried to compile it though!

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