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From: jafo@ariel.tummy.com (Sean Reifschneider)
Newsgroups: comp.os.linux.development.system,comp.unix.bsd.freebsd.misc
Subject: Re: Ideal filesystem
Date: 22 Mar 96 19:48:20 GMT
Organization: tummy.com, ltd.
Lines: 55
Message-ID: <31530404.0@sylvia.tummy.com>
References: <4hptj4$cf4@cville-srv.wam.umd.edu> <3140C968.20699696@netcom.com> <4isubc$ri9@floyd.sw.oz.au> <4itvde$492@narses.hrz.tu-chemnitz.de>
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Xref: euryale.cc.adfa.oz.au comp.os.linux.development.system:19852 comp.unix.bsd.freebsd.misc:15849
In article <4itvde$492@narses.hrz.tu-chemnitz.de>,
Andre Fachat <fachat@physik.tu-chemnitz.de> wrote:
>I have once seen a concept that hides a directory, in that it makes
>it look like a normal file. This was used for _binaries_, on a machine
>with multiple - different! - CPUs, that had access to the same
>filesystem and actually running _one_ OS.
This was what HP called a Context Dependant File (CDF) and was done by
changing a directory's SUID bit. You could access the directory by
appending a '+' to it:
$ mkdir test
$ chmod 4755 test
$ ls -a
. ..
$ cd test
'test': No such file or directory.
$ cd test+
$ ls -a
. ..
$ touch MC_68020 # assuming you are on a 68020 or greater machine
$ cd ..
$ ls -a
. .. test
$ cat test
$ # Nothing in test.
You could name the "CDF" entries by either processor type (great for machines
that had several types of binaries on them) or by machine name (you could have
a different .profile for each machine that a directory was shared to).
CDFs were created for HP's "clustering" or discless UX (DUX). You could have
a cluster of RISX and CISC machines where "/usr/local/bin" had the appropriate
files for each type.
Something similar could be done with "tagged" CDFs where you could have:
ARCH=i386 # 386 or higher executables
ARCH=i586 # pentium optimized executables
LANG=english # english language options
HOST=foobar # matches a given host
etc...
That could be fairly useful, but then you get into issues of how do you
distribute that information via NFS, and backup utilities have to be
able to handle it (HP added options to TAR, CPIO, and their backup
tools that made it handle CDFs as directories, but they weren't the
default).
Sean
--
"We just wanted to give the band a little more thrust than most other bands."
- Donald Fagen's reply to why they chose the band name 'Steely Dan'
Sean Reifschneider, Inimitably Superfluous <jafo@tummy.com>
URL: <http://www.tummy.com/xvscan> HP-UX/Linux/FreeBSD X11 scanning software.