UNIX continues!

[trb at floyd.UUCP]

I made an amazing discovery the other week, and I confirmed it a few
minutes ago.  It's possible to CONTINUE 4.1bsd UNIX sometimes after it
HALTs.

About a month ago, my 780 hung for no evident reason, it was not
echoing characters, it was just cycling with the little green light
on.  I was destined to HALT it and then reboot it and fsck it, which
would have taken 15-20 minutes and lost a bunch of work, so I figured
that nothing horrible could happen if I HALTed it and tried to CONTINUE
it.  So I hit ^P and got a >>> prompt, typed HALT, got a HALT message
and another >>>, then I typed CON and floyd came right back, hot to
trot, processes still running, etc.  No fsck, no nothin!

I told this to my esteemed colleague harpo!ber and he told me to go
play in traffic.  Well, ber isn't here today, and harpo HALTed without
a UNIX message for some unknown reason.  Debbie Manning, harpo's
operator, was pretty upset, and I said hold on.  I typed CON to the >>>
and harpo came right back to life!  Enough to make you find religion.

Anyway, I know that CONTINUING after HALTs isn't the solution to OS
bugs, but I figure that if I can CONTINUE after a HALT which offers no
other evidence, and if doesn't HALT again, then it's a pretty good
idea.  I'd appreciate it if other people would share their impressions
and experiences on this matter.

	Andy Tannenbaum   Bell Labs  Whippany, NJ   (201) 386-6491