Subject: Re: HEADS UP: migration to fully dynamic linked "base" system
To: NetBSD-current Discussion List <>
From: Johnny Billquist <>
List: current-users
Date: 08/27/2002 02:03:26
On Mon, 26 Aug 2002, Greg A. Woods wrote:

> Ah, no, right in /usr, as in this example from the V7 distribution tape:
> 	root:VwL97VCAx1Qhs:0:1::/:
> 	daemon:x:1:1::/:
> 	sys::2:2::/usr/sys:
> 	bin::3:3::/bin:
> 	uucp::4:4::/usr/lib/uucp:/usr/lib/uucico
> 	dmr::7:3::/usr/dmr:
> "dmr" being of course a default account for Dennis Ritchie.

I don't care to check up on a V7 system right now, but I seem to remember
that /usr/home was pretty common by then, even if dmr still hang around in

> > 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.

Yes, that is a funny migration, I admit. But already in V7 you had
/usr/bin, /usr/lib, and so on...
And that, I believe, was true in V6 as well.

> 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).

Ah, the "modern" approach. Well, I still want to have a small and simple
root file system, with as little crud as possible. For me, the root file
system would ideally be mounted read-only. Under /usr, things have a
little more tendency to change, but I guess I *could* mount a lot of
different directories one level below that if things were looking that

> > 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).

RP04/05/06 were definitely hot stuff in the late 70:s, but V7 usually
expected a massbus disk in order to function. RK05 were out of the
question by 1975.
The "original" system? If you mean the PDP-7 in 1969, it defnitely didn't
have any massbus disks, but then again, it didn't have pipes either. And
almost not anything else you recognize either.
-71 or -72, when the first porting to the PDP-11 was done, things were
still looking very different from today. By V5, you got memory management,
and disks started to grow bigger, but then we're up to about V5, when
things started looking somewhat familiar.

Like I said, disk partitions didn't enter the picture until you had larger

> 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.

Definitely true.

> 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.

Problem is, some parts of the system files change a lot more often than
other parts. And then we have yet another good reason. Sometimes buggy
programs makes partitions fill up (and sometimes disk fill up even
without bugs). You don't want the wrong partitions to fill up, because
then you might have problems.

I've seen that on unnumbered occasions with people who have everything in
one partition or two.


Johnny Billquist                  || "I'm on a bus
                                  ||  on a psychedelic trip
email:           ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol