Hi Jim,
Not all your guesses were correct, but you did guess the real
problem.  Many, many thanks.  We only changed the ip number on our
Linux server, not the kernel level.  However, after your post I
checked /dev and all the device special files were gone.  /proc/scsi/
IBMchanger and /proc/scsi/IBMtape still existed.  I re-installed
lin_tape, and that re-created the missing files.  Life is back to
normal.

We have rebooted this server in the past without this effect.  If
changing the ip number is orthogonal to losing the device files, what
else could be the cause?

Again with my thanks and best wishes,
Keith Arbogast
Indiana University