Bill On Wed, Mar 20, 2013 at 6:16 PM, Bill Pechter <pechter at gmail.com> wrote: I'd kill to see the sources for dual universe Unix so I could look to see about implementing a BSD/Linux dual universe clone... I'm mostly a sysadmin -- but I'm crazy. It's not that hard. I wrote that code in a weekend for Masscomp. It's one system call to set it, and then a number of places in the kernel to use it. Send me email offline, and I'll explain in more detail if you like. I did it on a bet with Gourd to prove it could be done. Then Bonnie Johnson picked up on it and showed it the late Lorin Gale (VP of Eng) . We sold it to marketing as a solution BSD vs AT&T "UNIX Wars" that was going around. As you said, Pyramid took it way farther than we did. We looked at it a crutch, so we could bring code in from other flavor. I think it's interesting that HP took the attitude of keeping their BSD based kernel (like we had at Masscomp) and spliced System V on top of it, including using the System command system and then claiming they were System V. Sun would try to mate with AT&T and we all know how well that worked ;-) Truth is there are better ways to do that these days that the idea of Universes. While they did exist in the research community at the time, the microkernel was nascent. I know tjt and I were aware of them, using a ukernel was not a popular way to build systems in those days. Particularly since, we were worried about real time so I suspect we rejected it, because we would have thought the extra code path / system delay to be detrimental. Remember, RSX, RT11 and VMS were Masscomp's "competition." That said, in amazes me that today, Linus still rejects the idea of ukernel. The benefits are so much better than the cost, and tricks like universe are not needed and IMO easier to manage. To this day, if I have to deal with Winders, I install whatever MSFT calls "SFU" these days - where is the posix system call layer and Unix utilities for the NT ukernel. As much as I am a fan of what Linux has done for the market (because I'm basically a UNIX junkie at heart), I personally think that it is interesting to note that the most popular OSs in total installed base (Winders, MacOS and iOS) are based on uKernels and only Linux is a hold out. BTW: It's been done by others, but if you want something cool to try, take Darwin (which is an FreeBSD/Mach blend and what both iOS and MacOS sit on), and build a Linux "personality." A couple of years ago, a few of us were toying with trying to splice VMS system call layer on top of Darwin (You'd pickup all the support for x86 family for free, you'd get compilers and tools). But one of the people involved soured a number of us when said party would not listen to rest of us. After a number of us dropped out, I think the idea fell apart. Clem