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diff --git a/faq/old_hurd_faq.txt b/faq/old_hurd_faq.txt new file mode 100644 index 00000000..4ebe019b --- /dev/null +++ b/faq/old_hurd_faq.txt @@ -0,0 +1,145 @@ +The Unofficial (and no longer maintained) GNU Hurd FAQ, Version 0.13 + +Contributions by: + +Michael I. Bushnell <mib@gnu.org> +Len Tower <tower@gnu.org> +Trent Fisher <trent@gnurd.uu.pdx.edu> +jlr@usoft.spb.su +Remy Card <Remy.Card@masi.ibp.fr> +Louis-Dominique Dubeau <hallu@info.polymtl.ca> + +Original Document by: Derek Upham <upham@cs.ubc.ca> + + +============================== + +Contents: + +Q0. Where can I get the Unofficial GNU Hurd FAQ? +Q2. Where can I get a copy? +Q3. Why bother writing a new OS when we have Linux and 386/BSD? +Q4. What's all this about Mach 3.0 (and Mach 4.0)? +Q5. Where can I find more information? +Q7. What sort of machines will run Hurd in the future? +Q8. What is the current development status? +Q9. What sort of system would we have if the Hurd was bootable today? + +============================== + +Q0. Where can I get the Unofficial GNU Hurd FAQ? + +The Unofficial Hurd FAQ (what you are reading now) is occasionally +posted to the USENET newsgroup, gnu.misc.discuss. It is also +available from + + http://www.enci.ucalgary.ca/~gord/hurd/hurd-faq.txt (Broken Link ?) + +If you don't have WWW access, you may send mail to me, Gordon +Matzigkeit <gord@enci.ucalgary.ca> with a subject line that reads: + + Subject: send hurd-faq + +You should receive a PGP-signed copy of the current version of this +document in a matter of minutes. + + +Q2. Where can I get a copy? + +To put it simply, you can't. It is still under development (by +Michael Bushnell, Roland McGrath and Miles Bader). It is almost, but +not quite, at the point where you can do real work on it. Keep your +fingers crossed. + +Some people have actually bootstrapped it, but the work is not easy, +and the current snapshot won't work until a new multiserver boot +mechanism is made. + +If you *really* want to try it, beware that it is still pre-alpha +code, and that it will likely crash on you. See Trent Fisher's Hurd +pages (under question 5) for the latest information. + + +Q3. Why bother writing a new OS when we have Linux and 386/BSD? + +For one thing, Linux and BSD don't scale well. Hardware designers are +shifting more and more toward multiprocessor machines for performance, +and standard Unix kernels do not provide much multiprocessor support. +The Hurd, on the other hand, runs on top of the Mach 3.0 micro-kernel +[[1]] from CMU. Mach was designed precisely for multiprocessing +machines, so its portability should carry over nicely to the Hurd. + +In addition, the Hurd will be considerably more flexible and robust +than generic Unix. Wherever possible, Unix kernel features have been +moved into unprivileged space. Once there, anyone who desires can +develop custom replacements for them. Users will be able to write and +use their own file systems, their own `exec' servers, or their own +network protocols if they like, all without disturbing other users. + +The Linux kernel has now been modified to allow user-level file +systems, so there is proof that people will actually use features such +as these. It will be much easier to do under the Hurd, however, +because the Hurd is almost entirely run in user space and because the +various servers are designed for this sort of modification. + + +Q4. What's all this about Mach 3.0 (and Mach 4.0)? + +As mentioned above, Mach is a micro-kernel, written at Carnegie Mellon +University. A more descriptive term might be a greatest-common-factor +kernel, since it provides facilities common to all ``real'' operating +systems, such as memory management, inter-process communication, +processes, and a bunch of other stuff. Unfortunately, the system +calls used to access these facilities are only vaguely related to the +familiar and cherished Unix system calls. There are no "fork", +"wait", or "sleep" system-calls, no SIGHUPs, nothing like that. All +this makes it rather difficult to, say, port GNU Emacs to a Mach box. + +The trick is, of course, to write an emulation library. Unix programs +can then use (what they think are) POSIX system calls and facilities +while they are really using Mach system calls and facilities. + +The simplest way of going about this is to take an ordinary Unix +kernel, open it up, and rip out all the machine-specific guts; any +time the Unix kernel talks to the machine, replace the code with calls +to the Mach micro-kernel. Run this fake kernel on a Mach machine and +you end up with something that looks and acts just like Unix (even to +GNU Emacs). Note that the Unix kernel we have implemented is just one +Really Big Mach program (called a single-server). + +The Hurd, on the other hand, breaks the giant Unix kernel down into +various Mach programs running as daemons. Working in concert with +facilities placed in the C library, these daemons provide all of the +POSIX system-calls and features; from the outside they look just like +a standard Unix kernel. This means that, for practical purposes, +anything that you can port to Linux will also port to the Hurd. + +Of course, if a user wishes to run his own daemons, he can do that as +well.... + +Mach 4.0 is an enhanced version of Mach 3.0, put out by the people at +the University of Utah. They are working on another free operating +system, and part of it includes an enhanced, more flexible version of +Mach. The Hurd has moved to Mach 4.0, which is good, because it is a +lot easier to build than 3.0 was. + +You can find more information on Mach by browsing the Hurd pages given +in the next answer, or by looking at the Project Mach and Flux +homepages at: + +Carnegie Mellon University (for Mach versions before 4.0): + + http://www.cs.cmu.edu/afs/cs.cmu.edu/project/mach/public/www/mach.html + +the University of Utah (for Mach 4.0): + + http://www.cs.utah.edu/projects/flux/mach4/html/ + + + +============================== + +Footnotes: + +[[1]] Yes, I know that ``micro-kernel'' is about as apt a description +as ``Reduced Instruction Set Chip'', but we're stuck with it. |