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Pretty much everything "unix" these days is actually Unix-like, but would it be possible to write an actual UNIX system, that is based off the original codebase, that would be a truly "modern" OS (e.g., 64-bit, multi-processing)?

What, like Solaris? Or the various BSDs?

Yes, I guess I should be more clear: would it be possible to make an open-source hobby OS, not a commercial one, that is actually UNIX?

What, like FreeBSD?

BSD has (to my knowledge) been rewritten to the point of not containing a single line of AT&T code.

But the original AT&T code is copyright. You couldn’t use it in an open source OS.

illumos is a fork of when Solaris was open source. That is about as close as you can get to an open source true Unix.. TBH though, I'm sure there isn't any AT&T code left.

Just as an aside, if we are talking about the original Unix code base, it was written in PDP11 assembly language. It’s difficult to think that that code would be very relevant today.

The very most original Unix code base was in PDP-7 assembly language, but that and the early PDP-11 releases were completely internal to Bell Labs and only ran on a few machines ever. By the time Unix was unleashed upon the world, it was written mostly in C.

v6, v7, (PDP-11) and 32v (the VAX port of v7) are now under BSD-style licenses. System III and later are still proprietary.

Hi Pavel,



The tuhs project might be of some interest to you. https://minnie.tuhs.org/cgi-bin/utree.pl

xv6 is something you may find interesting as well.

RetroBsd might interest you too.
https://github.com/RetroBSD/retrobsd

Another interesting approach might be to get old unix'es working on new risc v boards as a proof of concept.
See this project for instance.
https://github.com/mit-pdos/xv6-riscv


~Voldemort~