Subject: Re: HEADS UP: migration to fully dynamic linked "base" system
To: None <>
From: Greg A. Woods <>
List: current-users
Date: 08/26/2002 18:03:03
[ On Monday, August 26, 2002 at 20:22:14 (+0200), Johnny Billquist wrote: ]
> Subject: Re: HEADS UP: migration to fully dynamic linked "base" system
> On Mon, 26 Aug 2002, David Laight wrote:
> > > And to keep libraries where they have traditionally belonged (ie, in
> > > /usr/lib) and only there.
> > 
> > How old is tradition?
> > 
> > I'm sure the first unix system I used had users filestore in /usr
> > (ie home directories).
> /usr/home I'd suspect.

Ah, no, right in /usr, as in this example from the V7 distribution tape:


"dmr" being of course a default account for Dennis Ritchie.

> Is there anything wrong with that? I occasionally still wan't to place it
> there. Seems rather sensible.

Well, the point, I think, is that /usr began as a place for user's files
and ended up as a place (at least in hier(7)) where only system files
normally live.

Today there's no reason other than tradition for putting system files in
/usr in most circumstances any more -- most disks on any usable system
today are big and fast enough that having all the system files in one
filesystem is trivial (even if you use LDSTATIC=-static everywhere).  My
smallest usable i386 system (which does have /usr stuff dynamically
linked) fits comfortably in a 200MB root filesystem, with a separate
disk for /var and of course a memory filesystem for /tmp, though it
could be loopback mounted on /var/tmp in multiuser mode if RAM was
really short).

> That was not the only, or even main reason. Even an RP06 holds 176 megs,
> and those were the *old* days, and that was a rather common disk on
> PDP-11s in those days.

You should do some deeper diging into the actual history of Unix.  If
there had been an RP06 on each of the original systems used by Ken &
Dennis et al and if such a large disk had been common-place on the
hardware they decided to support for their original OS distributions,
then I'm sure we'd have a very different "tradition" today.  RP06 was
the high end back then (1979 for V7, for example).

Of course one of the more important reasons for separate filesystems,
and still a relatively important one today, is for reliability.  A
quiescent filesystem is much less likely to be damaged on a crash.
Therefore if you keep all the system files on one filesystem and all the
user files on another (or others) then it's less likely that the system
files will be damaged by a badly timed crash of any kind.

								Greg A. Woods

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