various boot-related questions.

[Ruth Milner]

In article <41737 at sgi.sgi.com> jmb at patton.sgi.com (Jim Barton) writes:
>We don't autoreboot after an OS crash because there may be
>important data sitting on the screen that would be lost in this case - like
>the error message which tells you what happened.  

I have been using this argument to justify hardcopy consoles since the day
we set up our first UNIX system. Why do none (as far as I know, anyway) of
the UNIX-box vendors suggest or sell a hardcopy console for just this
reason? It's so much more useful than a 24-line screen.

>You can't get the final crash messages from SYSLOG!  The kernel just crashed,

>From /usr/adm/oSYSLOG:

Sep 11 08:06:32 irides.physics PANIC: CPU 0: assertion failure!

Granted, this is put there by savecore, but it is still available. There was 
not much more than that on the screen. Really serious crashes will mean the 
system can't reboot anyway, and there will still be information on the screen 
about why.

>filling up swap won't crash the machine, the OS will instead start gunning
>down processes.  

I've seen it with my own eyes. It can happen. I don't know whether it was
because the kernel needed to run something and couldn't get the swap, or
whether it "gunned down" a process it probably shouldn't have and got a panic, 
but it has happened to us. Further to this subject, I'd be interested to
know how it decides which processes to destroy. The biggest ones? The newest
ones? The lowest-priority ones ... ?


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 Ruth Milner          UUCP - {uunet,pyramid}!utai!helios.physics!sysruth
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