Thanks to everyone for your responses and input.  In answer to (I think)
Colin's question:

> what kernel are you using?

GENERICSBC-56 (from the kern_sbc.tgz file).


I decided to try to rebuild the system from within NetBSD, and booted it
up.  No getty as it went into multi-user (oops, guess what I forgot to do?)
and hung.  On reboot, the /usr partition realized that it did indeed have
filesystem damage (I should note that /usr was the only partition that had
problems).  It took three passes of fsck -fy to clear it all up!  Many
files and programs were lost, including the all-important tar.

I was also missing sed, so the PPP kit wouldn't work.  I downloaded the
base.tgz tarball into another system where I have an account and extracted
tar, sed, and ld.so (which was needed by many other programs).  Once I was
able to bring up a PPP link, I downloaded all the tarballs and extracted
them... but I had to wipe /usr/include because the files were horribly
scrambled -- files thought they were directories, etc.

After a successful extraction, I edited /etc/fstab to make the root and
/usr partitions read-only.  Maybe that will slow down future problems.

Anyway, I learned about *some* of the absolutely critical files needed
to operate NetBSD.  And if you can just get Humpty Dumpty up to single-
user, you have a good chance of putting him back together again. :-)

--
Larry Kollar    | Dawson County GA, Tandy 600, WordBasic pages at:
kollar@stc.net  | http://www.nyx.net/~lekollar/