Date: Sun, 09 Jul 2000 16:12:36 -0400 From: John Baldwin <jhb@FreeBSD.org> To: Arcady Genkin <antipode@thpoon.com> Cc: freebsd-questions@FreeBSD.ORG Subject: Re: Automatic reboot out of the blue. Message-ID: <3968DCB4.C274A2D5@FreeBSD.org> References: <200007092146.OAA00558@john.baldwin.cx> <87hf9z2c37.fsf@tea.thpoon.com>
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Arcady Genkin wrote: > > John Baldwin <jhb@FreeBSD.ORG> 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 <jhb@FreeBSD.org> To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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