Re: Dumping kernel log (dmesg) and backtraces after a panic

[Arjan van de Ven]

On Sat, 2004-08-21 at 04:21, Chris Johns wrote:
> We're using Red Hat EL3 Linux (2.4.21 base kernel plus 300 or so Red 
> Hat and/or community patches) and I'm dearly missing KDB already, since 
> we previously used 2.4.21 from kernel.org and applied the appropriate 
> KDB patch(es). Now with EL3, I'm not even sure what the right patch for 
> KDB would be.
> 
> The problem is how to debug a hang or panic without KDB. Specifically, 
> I'd like to dump out real backtraces of all (or selected) processes 
> instead of the pseudo-backtraces that the panic or Alt-Sysrq-t 
> provides, and I'd like to dump out the kernel log buffer (dmesg) after 
> a hang or panic.
> 
> When I say "pseudo-backtraces", it seems that the oops/sysrq processing 
> picks everything that looks like a text address from the stack of each 
> thread (or the thread that caused the panic) and formats it, rather 
> than walking the stack back correctly like KDB's 'bt' command does. And 
> I don't know of any way of getting the 'dmesg' output after a 
> hang/panic other than by using KDB.


why not use netdump and then analyze the dump on another machine with
"crash" (a gdb variant) ?

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