From owner-freebsd-questions@FreeBSD.ORG Tue Nov 25 20:02:32 2008 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id DD9861065670 for ; Tue, 25 Nov 2008 20:02:32 +0000 (UTC) (envelope-from freebsd-questions-local@be-well.ilk.org) Received: from mail5.sea5.speakeasy.net (mail5.sea5.speakeasy.net [69.17.117.7]) by mx1.freebsd.org (Postfix) with ESMTP id B81508FC1E for ; Tue, 25 Nov 2008 20:02:32 +0000 (UTC) (envelope-from freebsd-questions-local@be-well.ilk.org) Received: (qmail 18681 invoked from network); 25 Nov 2008 20:02:32 -0000 Received: from dsl092-078-145.bos1.dsl.speakeasy.net (HELO be-well.ilk.org) ([66.92.78.145]) (envelope-sender ) by mail5.sea5.speakeasy.net (qmail-ldap-1.03) with SMTP for ; 25 Nov 2008 20:02:32 -0000 Received: by be-well.ilk.org (Postfix, from userid 1147) id AFF895087C; Tue, 25 Nov 2008 15:02:30 -0500 (EST) To: Frank Solensky References: <1227635054.6253.16.camel@frank-laptop> From: Lowell Gilbert Date: Tue, 25 Nov 2008 15:02:30 -0500 In-Reply-To: <1227635054.6253.16.camel@frank-laptop> (Frank Solensky's message of "Tue\, 25 Nov 2008 12\:44\:14 -0500") Message-ID: <44iqqb4lrd.fsf@be-well.ilk.org> User-Agent: Gnus/5.11 (Gnus v5.11) Emacs/22.3 (berkeley-unix) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: freebsd-questions Subject: Re: Kernel crash before dumpon X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 25 Nov 2008 20:02:32 -0000 Frank Solensky writes: Wow. Frank Solensky. Long time no see. > I'm trying to get a dump off a machine with a 7.1-beta2 kernel that's > been crashing during the boot process, following the instructions on > http://www.freebsd.org/doc/en/books/developers-handbook/kerneldebug.html#KERNELDEBUG-OBTAIN > I've recompiled the kernel with "-g" but no vmcore file appears so I'm > assuming that the crash occurs before dumpon is executed. > > The page includes the following suggestion on how I might be able to > proceed: > Alternatively, the dump device can be hard-coded via the > dump clause in the config(5) line of a kernel configuration > file. This approach is deprecated and should be used only > if a kernel is crashing before dumpon(8) can be executed. > > I tried adding > config dump "/dev/ad4s3b" > to the configuration file but that option appears to be no longer > supported: the config command gives an error message of: > root/dump/swap specification obsolete > > Is the paragraph above obsolete? If so, what's the preferred way to > collect the dump? Yep, it looks like the config(8) code to handle that has been gone for a while. At a quick glance, I can't figure out where the dump device is chosen, but it's supposedly iterating through devices looking for something that would work. Sticking in a device closer to the top of the search order might help. I suppose it's possible that just sticking in an appropriately formatted USB disk might help. Enabling minidumps would let you get away with a smaller space for storing the dump, which would be useful if you have some space to throw at it. Alternatively, in the same spot I would be tempted to build a separate disk just for debugging this particular problem, making sure to leave space for a swap partition close to the front. Using DDB might be an option, but I suspect that if you're having trouble getting a dump, you'll have problems dropping to a live debugger as well. All of my above advice is a bit shot-in-the-dark; if no one else suggests anything better, you may want to go to the freebsd-hackers list, or look at the cvs logs for whoever's modified the dump code in the last year or so. Good luck. -- Lowell Gilbert, embedded/networking software engineer, Boston area http://be-well.ilk.org/~lowell/