Stupid man pages

[Bob Goudreau]

In article <1990Jun12.145231.25545 at nbc1.ge.com>, scott at nbc1.ge.com
(Scott Barman) writes:
>>>
>>>In addition to error message, Sun continues to move things around to
>>>the point they it is getting real annoying.  Like /usr/spool being a
>>>symlink to /var/spool?  Why not just keep /usr/spool as it has always
>>>been?  Another one would be to load SunOS 4.* and cd to /usr/lib/uucp
>>>and not find everything there because THEY decided the configuration
>>>stuff belongs in /etc/uucp after it has live in /usr/lib/uucp for all
>
>...
> 
> You're right, users do not notice the change.  But I am not a full time
> systems administrator and I have better things to do (including meeting
> deadlines) than to hunt down things that have been in a "standard"
> place since I learned Unix under v7.  I still would like to know the
> motivation!

Actually, the motivation is fairly reasonable, and the implementation
makes a lot of sense.  Files and directories weren't moved gratuitously,
but only in pursuit of specific goals.

The most important capability gained by reorganizing files in this
manner is the ability to save disk space and make release management
easier by sharing most of the OS release files among multiple hosts.
In particular, a server machine and all its diskless clients can mount
the same /usr file system (the clients mount it read-only over NFS, in
fact) with no need to give each host its own copy.  The important
dichotomy here is "shared & read-only" versus "private & read-write".  
Shared stuff was moved to /usr; the (much smaller) set of private files
and directories that distinguish the "personality" of one system from
another were grouped together in the root (mostly in /etc and /var).
Under this setup, adding a new diskless client doesn't cost much disk
space on the server, since the only *new* space he needs is for his
own root and swap.

To give a concrete example of the differences between shared-RO data
and unshared-RW data, consider lpr and uucp.  The actual *programs*
used for printing and for uucp communication stay in /usr (because
they're shareable); actual print jobs and uucp messages are private to
a particular system, so they belong in /var/spool.  Likewise,
/usr/etc/termcap is shareable; /etc/motd is not.  Of course, symlinks
can be used liberally to ease the transition.  Just remember that
while many hosts may share the same symlink, the *target* of that
symlink is usually host-dependent.  For example, several diskless
clients can mount the same /usr and thus share the same /usr/spool
symlink, but the target of that link (/var/spool) will differ
depending on which host the pathname is getting resolved on -- each
host gets its *own* /var/spool.

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Bob Goudreau				+1 919 248 6231
Data General Corporation
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