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Date:      Thu, 20 May 2004 08:59:58 -0400 (EDT)
From:      Andrew Gallatin <gallatin@cs.duke.edu>
To:        Nick Strebkov <nick@humgat.org>
Cc:        hackers@freebsd.org
Subject:   Re: obtaining a kernel crash dump
Message-ID:  <16556.43982.226708.375607@grasshopper.cs.duke.edu>
In-Reply-To: <20040519133442.GA90053@nord.interexc.com>
References:  <20040519133442.GA90053@nord.interexc.com>

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Nick Strebkov writes:
 > May 19 16:17:00 devel /kernel: 
 > May 19 16:17:00 devel /kernel: syncing disks... 60 3 2 
 > 
 > [dd boot kernel messages]

Try disabling sync-on-panic.  It almost always causes problems for me
when trying to get dumps.  

% cat /etc/sysctl.conf 
kern.sync_on_panic=0

If you are running a newer version of FreeBSD with the DDB_TRACE
options, you want to enable DDB and DDB_TRACE.  This will get you a
stack trace on console, which is a heck of a lot better than nothing
if your crashdumps don't work.

options         DDB                     #Enable the kernel debugger
options         DDB_TRACE


Sometimes I have problems getting a dump on 5.x if I've dropped into
ddb, so I use the following to prevent the system from dropping to a
DDB prompt at panic:

options         DDB_UNATTENDED



Drew



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