[TUHS] Abstractions

[Greg A. Woods]

At Tue, 23 Feb 2021 12:37:57 -0700, "Nelson H. F. Beebe" <beebe at math.utah.edu> wrote:
Subject: Re: [TUHS] Abstractions
>
> The recent discussions on the TUHS list of whether /bin and /usr/bin
> are different, or symlinked, brought to mind the limited disk and tape
> sizes of the 1970s and 1980s.  Especially the lower-cost tape
> technologies had issues with correct recognition of an end-of-tape
> condition, making it hard to span a dump across tape volumes, and
> strongly suggesting that directory tree sizes be limited to what could
> fit on a single tape.

Hmmmm... you may just be mixing up the names of the archive tools you
mean, but on the other hand maybe you don't know that "dump" does whole
filesystems, not just sub-directories.

That of course doesn't take anything away from what you were saying
about making sure you could do a full dump onto a single tape with some
types of less high-end and high-quality tape devices.  But that's a
"newer" problem.

Original Unix dump(1m) had no trouble asking for additional tapes to be
mounted when the filesystem required multiple tapes.

So it has nothing to do with legacy of the original root and /usr split.


> I made an experiment today across a broad range of operating systems
> (many with multiple versions in our test farm), and produced these two
> tables, where version numbers are included only if the O/S changed
> practices:

An interesting compilation, but sadly (to me at least) it is mostly a
mess of GNU/Linux which, rightly or wrongly, I categorize all under one
(extremely opaque) umbrella.

BTW, when I said "long ago" for Solaris, I meant a REALLY long time ago.
/bin has been a symlink to /usr/bin since Solaris 2.0 and yet /usr
could/can still be a separate filesystem on a Solaris installation.
This is accomplished by putting everything necessary to boot the system
up to the point where other additional filesystems can be mounted using
just the programs found in /sbin.  Of course this wasn't done smoothly
and completely all in one go.  IIRC /sbin/sh didn't exist until
Solaris-9, and (also IIRC) it is just a copy of /usr/bin/sh.

So Sun pushed everything in /bin to /usr/bin, then copied a few things
back to /sbin as they found they needed them.  Kind of a half-assed hack
that wasn't well thought out, and had very poor motivations.

I'd forgot that IRIX was following Solaris on this track.

--
					Greg A. Woods <gwoods at acm.org>

Kelowna, BC     +1 250 762-7675           RoboHack <woods at robohack.ca>
Planix, Inc. <woods at planix.com>     Avoncote Farms <woods at avoncote.ca>
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