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Date: Tue, 20 Jan 2004 20:34:09 -0800 (PST)
From: Don Lewis <truckman@FreeBSD.org>
To: rwatson@FreeBSD.org
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Subject: Re: cvs commit: src/sys/alpha/alpha support.s src/sys/i386/i386   
 swtch.s src/sys/kern kern_shutdown.c src/sys/sys systm.h
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On 20 Jan, Robert Watson wrote:
> 
> On Tue, 20 Jan 2004, Don Lewis wrote:
> 
>> It would be extremely helpful to preserve the panic message and
>> (optionally) the backtrace across the reboot.  Crash dumps may not
>> always be possible for any number of reasons (swap smaller than RAM,
>> /var/crash too small or overflowing with previous crash dumps, crash
>> dump takes too long ...).  This is especially true in cases where the
>> machine crashes and reboots unattended. 
> 
> Actually, I was having a very similar conversation with Bill Paul this
> afternoon.  We were discussing dropping a copy of the kernel message
> buffer onto the header of swap space on panic, if possible, and then
> dropping them in /var/log/crash.log for management by newsyslog.  Then the
> natural response to "My machine spontaneously reboots" becomes "Look for
> something recent in /var/log/crash.log", as opposed to "You'll need to
> enable crash dumps, set up a serial console", etc.  It's also something we
> could turn on by default, as opposed to crash dumps, which would otherwise
> consume of alot of disk space.

That is pretty much what I was thinking of as well, though I thought it
should be at the end.  I believe that we now swapon early, before fsck,
which has to happen before we mount /var ...