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+[[!meta copyright="Copyright © 1999, 2006, 2008, 2010, 2013 Free Software
+Foundation, Inc."]]
+
+[[!meta license="""[[!toggle id="license" text="GFDL 1.2+"]][[!toggleable
+id="license" text="Permission is granted to copy, distribute and/or modify this
+document under the terms of the GNU Free Documentation License, Version 1.2 or
+any later version published by the Free Software Foundation; with no Invariant
+Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license
+is included in the section entitled [[GNU Free Documentation
+License|/fdl]]."]]"""]]
+
+The Unofficial (and no longer maintained) GNU Hurd FAQ, Version 0.13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>
+
+
+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.