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From: henry@utzoo.UUCP (Henry Spencer)
Newsgroups: comp.unix.wizards
Subject: Re: /usr a misnomer?  (was File System Kudzu)
Message-ID: <7788@utzoo.UUCP>
Date: Tue, 17-Mar-87 00:14:14 EST
Article-I.D.: utzoo.7788
Posted: Tue Mar 17 00:14:14 1987
Date-Received: Tue, 17-Mar-87 00:14:14 EST
References: <4923@brl-adm.ARPA>
Organization: U of Toronto Zoology
Lines: 31

> > In fact, /usr is really a misnomer since most users
> > usually live on a different file system.
> 
> I belive that /usr stands for "user service routines."

Unless somebody fibbed to me in the dim distant past, it's this way.  If
you look at really old Unix papers, like the original CACM paper (not the
updated variants of it in places like Unix manuals!), you will find that
the original Unix system had a small fixed-head disk and a larger disk of
more normal structure.  The fixed-head disk was fast -- by the standards
of the time -- but really small.  It made sense to put the root file system
on the fixed-head disk, but this meant that only the most heavily-used system
stuff could live there.  The big disk was mostly given over to the file
system where user files lived, dubbed /usr for obvious reasons.  So the
overflow from root went under various "users".  This is why the default
search path hits both /bin and /usr/bin, because only small and often-used
stuff could live in /bin.  This is why libraries are split between /lib and
/usr/lib, because only the very busiest library stuff could go on the root
file system.  This is why the sources are under /usr/src.  This is why an
occasional program like sort, which expects its temporary files to be BIG,
creates them in /usr/tmp instead of /tmp.  (Of course, more recent system
variants have often changed things around, so don't nit-pick if yours does
things a little differently -- *my* distribution tape came from Bell Labs,
not from XYZ Vaporboxes Inc. or Miskatonic U.)  And so forth.

Nowadays Unix systems seldom share file systems between user and system
files, but /usr as a place for system files lives on because of all of those
pathnames that would have to be changed.
-- 
"We must choose: the stars or	Henry Spencer @ U of Toronto Zoology
the dust.  Which shall it be?"	{allegra,ihnp4,decvax,pyramid}!utzoo!henry