From owner-freebsd-questions Sun Jul 9 16:11:59 2000 Delivered-To: freebsd-questions@freebsd.org Received: from server.baldwin.cx (server.geekhouse.net [64.81.6.52]) by hub.freebsd.org (Postfix) with ESMTP id F416D37B59F for ; Sun, 9 Jul 2000 16:11:55 -0700 (PDT) (envelope-from jhb@FreeBSD.org) Received: from FreeBSD.org (john.baldwin.cx [192.168.1.18]) by server.baldwin.cx (8.9.3/8.9.3) with ESMTP id QAA16474; Sun, 9 Jul 2000 16:11:50 -0700 (PDT) (envelope-from jhb@FreeBSD.org) Message-ID: <3968DCB4.C274A2D5@FreeBSD.org> Date: Sun, 09 Jul 2000 16:12:36 -0400 From: John Baldwin X-Mailer: Mozilla 4.51 [en] (Win95; I) X-Accept-Language: en,pdf MIME-Version: 1.0 To: Arcady Genkin Cc: freebsd-questions@FreeBSD.ORG Subject: Re: Automatic reboot out of the blue. References: <200007092146.OAA00558@john.baldwin.cx> <87hf9z2c37.fsf@tea.thpoon.com> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-freebsd-questions@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG Arcady Genkin wrote: > > John Baldwin writes: > > > Your kernel could have paniced, and the default behavior is to reboot > > when that happens. > > So there would not even be a log message in this case? In a kernel panic, we can't assume that anything in the system is working, as they only happen when really obscure error conditions occur that can't be recovered from. In that case, we can't write anything to disk for fear that we will corrupt data. We can dump our memory and kernel to the swap area (or whatever dump device is configured) so that it can be examined later, however. > > If you want, you can check the handbook section > > on kernel debugging to see how to compile a kernel with debug symbols > > (config -g) and to setup a dump device via dumpdev in /etc/rc.conf. > > Then, when your computer boots up after a panic, it will save a copy > > of the kernel and a memory dump to /var/crash/kernel.0 and > > /var/crash/vmcore.0. You can then use the kernel debugger as root > > to get some simple info and send an e-mail with it to -hackers. > > How much will this impair the performance? That box is barely enough > for what it's doing already (memory--wise). With an ELF kernel (such as we've had since 3.1), the debugging symbols are skipped over when the kernel is loaded, so the memory usage will stay the same. As far as the rest of performance, there may be some decrease, I'm not entirely sure. However, if there is I haven't noticed it as turning on debug symbols hasn't made any noticeable performance change in my machines. > Arcady Genkin > Thanks God I'm still an atheist! -- Luis Bunuel -- John Baldwin To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message