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``They are very different systems (personally, I think all of the current crop of kernels, including Darwin, have serious design problems).''
Agreed. I think if I were to hack on an existing microkernel today, I would probably go for VSTa rather than Mach.

``The phrase "purism" suggests that you think that this is some irrelevant ideological issue.''
Sorry for giving you the wrong impression, then. I don't think the issues are unimportant at all. I just don't agree with those who want everything to be GPLed (those I call GPL-purists). I understand companies' hesitation to release their source code, especially under something as irrevocable as the GPL. If they can't figure out a viable business model with that, they shouldn't do it. Of course it would be nice for us hackers to be able to Use the Source (WOW), and it might be better for the world, but that's not what drives companies in a capitalist environment.

If you want an open source microkernel, try vsta, or chaos, or openblt. And that's probably just starters.

The GNU HURD and
the VSTa systems are both GPL-ed systems which did borrow some ideas from Plan9.

Basile STARYNKEVITCH

Here's some critical analysis of it

That link don't work from where i'm standing.
http://www.zendo.com/vsta/
or others from google directory might be better...

Things people should be trying out include:

• VSTa
• Hurd
• MIT Exokernel
• SpinOS
• OSKit
• EROS
• Some variation on Wirth's Oberon systems

Even if you look at these, and go back to a UNIX-like system, there is benefit to seeing the extra abstractions they offer.

I'm not resisting "non-UNIX" things for the sake of them not being UNIX. Your conclusion that I am promoting "doctrinaire orthodoxy" comes from only half-reading the signature.

The point of the signature is that if you don't know the "orthodox," you are unlikely to do anything better than to merely replicate many of its features, badly.

It is also pretty fair to say that:

Any sufficiently complicated C or Fortran program contains an ad hoc informally-specified bug-ridden slow implementation of half of Common Lisp. -- Philip Greenspun

I think there should be a richer set of systems software research going on; people should be trying out EROS. People should be trying out And Hurd.

There should be work going on to provide OS environments supporting:

• Persistent data structures
• Garbage collected operating environments
• Filesystems with semantics going beyond the UNIX "bags of bytes."
• Security management using capabilities

Some of them will surely fail, and that's OK. Some of them may succeed, and that's a good thing.

One of the steps to allow people to actually learn from getting into system designs is to actually understand the systems that have come before.

In that light, it is not doctrinaire orthodoxy to consider that...

• Pricing.

  It is notoriously difficult to get pricing information for QNX.

  I have heard differing reports on comp.os.qnx, including that it is "very expensive, hundreds of dollars per system," or, on the other hand, the vague answer of "you can license it reasonably economically." (With no definition of what "reasonably economical" means, of course.)

• If people should start thinking of QNX, then they should also start thinking of:
  • VSTa

    A copylefted system that "lifts" ideas from QNX and Plan 9

    It looks like development has not been terribly active lately.

  • MIT Exokernel

    Again, not terribly active, but an interesting OS kernel.

  • EROS

    Eric Raymond thinks it's mindblowing, so the Eric Raymond Personality Cult should all be preparing to drop Linux in favor of EROS. (Of course, it isn't yet capable of self-hosting, which indicates that it's not all that useful at this point. But, to cultists, usefulness is irrelevant...)

  • Possibly even Hurd

    It's different from the other options; certainly not a tiny OS option...

  • eCos
  • RTEMS

    Which, like QNX, appears to be used in some reasonably critical system environments...

  • Fiasco

    Which is a "lighter microkernel than Mach"...

  • On Linux, people interested in QNX should almost certainly look at SRR -- QNX API compatible message passing for Linux

    This is the critical programming abstraction that QNX uses heavily which isn't all that widely used on traditional UNIXes, namely asynchronous messaging.

  These are all interesting alternatives, albeit not all being of identical levels of interest.

Of course microkernels suck, anyway.

-- Faré @ TUNES.org

Minix isn't all that horrible for what it is (a puny Unix that runs on small machines). I had it running on a PS/2 50Z with a 12Mhz 286 and was fully able to compile on of my pet projects on it. I was surprised that people still use it regularly, and that active development still occured (ie, a recent version can run off of a DOS partition). IIRC, it also comes with an Emacs wannabe, as well as C, Pascal, and Modula-2 compilers, so you can start hacking away!

386 users, though, might find VsTA more powerful and useful.

~~~~~~~~~
auntfloyd

Yes - not the fancy bits, but the kernel and major modules are re-created in VSTa (http://www.zendo.com/vsta). Development is not particularly active, but it works from a floppy with no problems.