There are really less than ½ dozen "Unix" OSes. 99% of them are variants on a theme.
#1
There's AT&T UNIX, including System V. That includes UnixWare, SCO OpenServer, Solaris and OpenSolarism and HP-UX .
Are any other SysV descendants still on sale?
#2
There's BSD.
That covers 4 FOSS BSDs I can think of offhand, plus AFAIK IBM AIX is derived from BSD. Anything else commercial?
#3
There's macOS. XNU is based on Mach. I can't think of any other current Mach derivatives. The HURD if you're generous.
#4
There's Linux, including Android and ChromeOS.
#5
There's QNX.
#6
There's Minix 3, which now mostly uses the NetBSD userland but has its own kernel.
Is that it?
Any other self-hosting, native on bare metal, Unix-like OSes?
I know a few things can emulate UNIX well enough to pass the Open Group tests if they cared to: IBM z/OS, OpenVMS. MS has 2: NT's POSIX environment, plus WSL1. But their native OS design is not Unix-like nor meant to be Unix-compatible.
Plan 9 isn't a UNIX although it is the one true direct offspring of UNIX. And Inferno is even less UNIX-like.
Serenity OS is not self-hosting and barely runs on bare metal.
HelenOS and Redox OS are only remotely superficially Unix-like.
Everything else is either dead, or historical and only runs in VMs or on emulators.
AIX is SysV-derived. IBM’s BSD was AOS (long discontinued).
> I know a few things can emulate UNIX well enough to pass the Open Group tests if they cared to:
The Open Group owns the UNIX trademark (they got it from AT&T via Novell), so legally they decide what it means. And they’ve decided it means the standard, and any system which implements the standard (how it does so is irrelevant), passes the test suite, signs the license agreement and pays the fees (which fund maintenance of the standard and tests) is UNIX. By that official definition (the only official definition), z/OS is just as much a UNIX as AIX is.
No problem and thanks for the clarification. FWIW I have been catching up with HN after a fortnight's holiday and I noticed a bunch of incisive and interesting comments from you, for which my thanks and congrats.
Any other SysV derivatives still on sale I haven't mentioned? Not sure I can think of any myself.
Re the UNIX™, yes, I know, and I've written about this a few times myself. Some Register readers got quite incensed with me. :-D
I think my point is clear enough though: if we consider the design and architecture, rather than compatibility, it is easy enough to distinguish Unix-like OSes that do not aspire or attempt Unix-compatibility from non-Unix-like OSes which either are, or are close to or formerly offered but no longer do, Unix compatibility... and I think that's a useful and important distinction.
Is there such a thing as a Unix “design and architecture” though? The architecture of Linux and XNU are quite different. Hurd even more so (as you say, if you count that). Later AIX versions moved to a much more standard architecture, but the original AIX (for the IBM RT-PC) ran on top of a microkernel (VRM) which was allegedly written in a PL/I dialect not C (the microkernel was shared between AIX and PICK OS, and you could run AIX and PICK simultaneously on the same machine, with the microkernel ensuring they didn’t step on each other’s toes). Historically, Unix was mostly about the APIs, not changeable details of how they are implemented internally. AT&T’s early 1980s port of Unix to IBM S/370 mainframes was essentially a compatibility layer running on top of IBM’s TSS/370 time-sharing operating system. That’s a very different architecture from most other Unixes, except maybe z/OS (although TSS and MVS were distinct IBM mainframe OS lines, the former now long discontinued), and Cray UNICOS’ ability to run as a guest under COS. Yet it is both a genetic Unix (based on the original code) and from AT&T themselves, so what sense does it make to say it isn’t “really” Unix? But if it counts, why not z/OS?
22. Unix History (levenez.com) 36 points by gandalfff 5 hours ago | flag | hide | 1 comment
What a coincidence
