Date: Sun, 15 Sep 2002 03:03:41 -0700 (PDT) From: Julian Elischer <julian@elischer.org> To: Sean Hamilton <sh@planetquake.com> Cc: hackers@freebsd.org Subject: Re: dmesg circular buffer Message-ID: <Pine.BSF.4.21.0209150259290.82711-100000@InterJet.elischer.org> In-Reply-To: <000501c25c99$af6b6d40$911de8d8@slugabed.org>
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On Sun, 15 Sep 2002, Sean Hamilton wrote: > Greetings, > > As I understand, "dmesg" prints the tail end of a circular buffer stored > someplace on the root partition. Is it possible to have it read back beyond > the last reboot? Occasionaly I see it do this, though I have no idea why. > > In this case, I have a kernel that panicked, and am looking for clues > Nothing in /var/log/messages... The buffer is the last N bytes of ram, and the housekeeping for it is with it.. If the BIOS doesn't clear it, it will last beyond a reboot. The incoming new kernel will recognise a valid buffer and continue to use it without overwriting teh old contents.. very useful after a crash. I often see this. It may be related with the 'quick boot' that some BIOS offer as an option. (takes less time if you do not clear RAM.) julian To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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