[lcall]

For some purposes, I wonder if OpenBSD would also be a strong candidate for learning about operating systems, given their focus on correctness, openness, portability, etc., and the fact that everything learned then becomes useful on a fully general-purpose OS that one could use in the long term (ie, lots of headroom, less need to start over for learning some things, somewhere else).

The quality and good order of the documentation in particular makes it less or not necessary to go doing web searches etc to find out how to do things, but they take one in an orderly progression from installation, via FAQs and excellent manual pages, all the way along to useful development info.

[Koshkin]

OpenBSD is huge (just like any general-purpose OS would be today). It's not a "teaching OS."

Minix would be a better alternative, IMHO.

[cat199]

agree - possibly any of the BSD's might be a good follow up for 'advanced' study since the codebase & kernel structures have a direct lineage. Maybe doing the 'base' course on like 4.2BSD which is still smaller and close to v7 might make sense

[beefhash]

4.4BSD-Lite2 is the earliest they could do without risking some legal issues[1].

[1] https://virtuallyfun.com/wordpress/2018/11/26/why-bsd-os-is-...

[vips7L]

Minix is still huge compared to xv6