[TUHS] Is there a good, even definitive, list of reimplementations of the Unix kernel? What would good cut-off criteria be?

[Bakul Shah via TUHS]

> On Apr 18, 2026, at 8:49 PM, Charles H. Sauer <sauer at technologists.com> wrote:
> 
> 
>> On Apr 18, 2026, at 9:52 PM, Bakul Shah via TUHS <tuhs at tuhs.org> wrote:
>> 
>> I believe Sol later merged into Chorus was a reimplementation in Pascal. I think this was a microkernel based system...
>> I believe Locus distributed OS designed at UCLA was also Unix compatible. I guess you can add Xinu as well as Amoeba to the list.
> 
> I intentionally never looked at Locus source, but had much interaction with Gerry Popek and Bruce Walker while I was at IBM and they were working with IBM. I have a memory of Bruce telling me they started with 4.1BSD, but I question that memory. Just glancing at their book (https://www.penguinrandomhouse.com/books/655167/the-locus-distributed-system-architecture-by-gerald-j-popek/), the only cited Unix reference I see is the 1978 Ritchie/Thompson BSTJ paper. Section 1.5 Unix Compatibility of their book says “For virtually all applications code, the LOCUS system can provide complete compatibility, at the object code level, with both Berkeley Unix and System V, …” I suspect that the first Locus prototypes were based on BSD earlier than 4.1.

Thanks. I have the Locus book but couldn't find it. If they started with BSD code, they must've had to do major surgery to achieve a distributed system! Except for bootstrapping & drivers probably easier to start from scratch....

I guess KeyNIX (atop KeyKOS) should be added as well: http://cap-lore.com/CapTheory/KK/UnixOnMicroKernel/