bill at hilfworks.com
Tue Jan 29 08:44:46 PST 2002
Robert Latham wrote:
> On Mon, Jan 21, 2002 at 06:13:44PM -0800, Martin Siegert wrote:
> > This is somewhat off topic - sorry for that.
> it's a great topic for clusters. in an ideal world, the kernel never
> oopses, but when you have N kernels and possibly dodgy hardware, it
> i get frustrated with this list because topics like Martin's get
> ignored, while topics like cooling with LN2, game console clusters
> and anything athlon get multi-day discussions.
> [snip problem report ]
> > The first thing I would like to do is to log the oops message. Right now
> > it goes to the console only - it does not appear in the log files
> > although syslog sends everything of severity *.info to /var/log/messages.
> i guess you've read Documentation/oops-tracing.txt , but if not, it's
> a good start.
> depending on where the panic happens, the part of the kernel that
> would normally write that oops out to disk doesn't run.
> So you've got a few options:
> . typing off the screen: sucks. a lot. and is highly error prone.
> and the kernel console blanking mechanism might kick in ( and since
> the kernel has paniced, it won't listed for input signals and unblank
> itself ) but if you've got no other option...
> ( one time a guy took a picture of the oops with a digital camera and
> sent that to me. that was fun. I don't have any character regognition
> software, but if someone knows of a linux OCR tool that won't mind a
> screenful of hex, i'd like to hear about it )
> . serial console: not bad. if it's just one machine, you can pass
> parameters to your kernel and capture all kernel messages over the
> serial port. Documentation/serial-console.txt has all the info you
> . netconsole: http://people.redhat.com/mingo/netconsole-patches/
> like a serial console, but using your network device instead of a
> serial device. It's a kernel patch and a convienece script for the
> sender and a userspace tool for the reciever to display the messages.
> Patching a kernel and setting up yet another tool might be a bit much,
> but man is it cool to see it work :>
> . patch your kernel to support "dump log to swapfile" or "dump log to
> disk". I haven't set something like this up, but always meant to
> try it out...
To expand on this, the Linux Kernel Crash Dump package:
and Dprobes (from IBMs Linux Technology Center):
... which can also be used with Opersys's Linux trace toolkit
And for the truly brave, use gdb ;)
> Basically the name of the game is to get that oops into a form you can
> feed to ksymoops, then hope the backtrace it prints out gives you a
> clue. ( like "oh, the last thing it called was do_scsi_service... maybe
> i have a dogdy scisi controller ).
> Anybody else know of good ways ( even funny bad ways might be
> entertaining) to capture an oops?
> Rob Latham
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<bill at hilfworks.com>
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