this book was a key stepping stone from being a support engineer on a product built on top of the bsd kernel, to becoming a developer on said product and launching a career as a software engineer with no formal college education whatsoever. OS internals were something I could touch and feel on a daily basis, and then I could read and comprehend the code that underpinned it all. Great stuff.

McKusick and Stevens will always be welcome guests on my bookshelf.

Yes, let us not forget our good friend TCP/IP illustrated: https://www.pearson.com/en-us/subject-catalog/p/tcpip-illust...

That and APUE are classics, RIP Mr. Stevens.

And not the Lions Book? https://en.wikipedia.org/wiki/A_Commentary_on_the_UNIX_Opera...

As mentioned Operating system design: the xinu approach is a great book

Ah yeah, The Design and Implementation of the 4.3BSD Unix Operating System, AKA "The Devil Book" in that scene in "Hackers" [1]

[1] https://www.youtube.com/watch?v=4U9MI0u2VIE

Nice to see the Multics book included on the Unix (related) list.

I'd like to see a non-Unix "alternative OS classics" list to supplement the Unix list.

Maybe a non-TCP/IP/Ethernet "alternative network classics" list as well.

Since these are mostly vintage (though nice reads) I'd also like to see a list of "modern (or future) systems classics" as well.

I would place the Windows Internals book series on that list, BeOS, Mac OS books from Apple (pre-OS X ones), Plan 9 books, Programming Inferno, for example.

Bitsavers has a lot of stuff http://bitsavers.org/pdf/

And 1000 bit has lots of brochures and old technical magazines.

https://www.1000bit.it/

It's not about any OS in particular, but Per Brinch Hansen has a book called Classic Operating Systems: From Batch Processing To Distributed Systems, which showcases a lot of historically important essays in operating system history. The back of the book says it "includes a bibliography of about 60 operating systems".

You can borrow it on archive.org: https://archive.org/details/isbn_9780387951133/mode/1up

Thanks to peer comments for the great suggestions.

NetBSD 1.0 under an emulated Vax (SIMH-Classic) would be the closest OS to apply the knowledge from the BSD 4.4 books.