Comment by sargstuff

On software side, building an OS (distribution) from scratch provides a step above bare metal programming[0].

Provides familiarity with different types of things a kernel does via programs/scripts that make use of kernel.

Actually writing binary code for kernel bit can be done under qem[1][2]. aka don't need to buy actual hardware, can use 'software probes' to view what's going on, etc. Don't have to worry about 'crashing'/trashing box running on (just crash the qem software & loosing just what was done in qem session, if didn't save as 'export/save to external location outside of qem session')

"Reading OpenBSD source code daily (blog.tintagel.pl)" from [hn: 3] automated way to review code.

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[0] : https://news.ycombinator.com/item?id=14521386