[TUHS] The origin of /home

Dan Cross crossd at gmail.com
Fri Sep 28 06:15:05 AEST 2018

On Thu, Sep 27, 2018 at 11:34 AM Noel Chiappa <jnc at mercury.lcs.mit.edu>

>     > From: Dan Cross
>     > particular in sites with lots of users like universities and
>     > production-focused corporate groups
> The existence of /usr, /usr/bin, /etc, /lib, etc dates back to the Research
> group at Bell, so I don't think we can look to these other environments
> for an
> explanation.

Sorry, I was (very) unclear in this point. I was referring to two separate

1) Why things were spread out across multiple filesystems (space and/or
performance considerations dating from the Bell Labs days), and
2) The notion that rigid structures built in at a very low level would
naturally give rise to local naming conventions as "large" sites grew
beyond the limitations built into the system. E.g., /udd/u1 etc vs /home vs
/usr/users vs /net/somehostname vs /var/users vs whatever. As a concrete
example is the use of name-dependent hierarchical home directory paths like
"/home/c/r/cross" because one tried to put too many directories into /home
(I have actually seen the UFS directory entry limit hit in /home on a
machine that had >32k users). Anyway, eventually through whatever accident
of history "/home" seems to have won as a de facto standard.

    > "Hmm. Well, we've got space in /usr: create /usr/bin
> I seem to recall reading (don't recall where, OTTOMY) an explanation for
> the
> creation of /usr/bin, and I think it was performance related; IIRC the
> issue
> was that they wanted to keep the directory size down (both for disk block
> caching, and search time, reasons). Or maybe that was later on, and it was
> originally created for 'user-maintained' ancillary programs (another vague
> memory)?

I think the latter might be a justification-after-the-fact: /usr as the
filesystem containing stuff of interest to the users.

    > The more intriguing possibility from the antiquarian point of view is
>     > whether someone coined "/home" and then THAT led to the rise of the
> "home
>     > directory" nomenclature.
> My memory is that the term "home directory" predates /home - perhaps on
> other
> OS's such as TOPS-20, but I don't have time to research that. (I did look
> quickly in the Multics docs, and it has 'working directory', i.e. current
> dir
> - but it refers to the home dir as 'original WD', i.e. the WD at the time
> of
> login.)

If I recall correctly, the mappings from "users" on TOPS-20 to directories
is an injection, but I don't think they used the "home directory"

Certainly the analogy with one's directory as home is clear enough.

        - Dan C.
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