Viewing dmesg output after crash

Hi

I'm debugging a system crash. I got OOPS message and found the buggy piece of code. I wish I had the output of dmesg just before the crash. In other words, I want to view the last messages collected by the ring buffer used by dmesg.

The log messages are certainly being appended to some logfile in the RAM. How can I find the address where the logfile is being created or how can I extract the logfile?

Thanks n Regards
Amit Virdi
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Hi Amit,

Truly, the easiest thing you can do is connect to the console via serial connection during boot and dump it that way.

The output you're getting from the boot probably isn't making it to logfiles yet.

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Bradley D. Thornton
Manager Network Services
NorthTech Computer
TEL: +1.760.666.2703 (US)
TEL: +44.203.318.2755 (UK)
http://NorthTech.US

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I use netconsole which sends the kernel ring buffer updates to a remote machine through UDP ..
And then you can use netcat command to dump the remote udp logs to a file and view it.
I have never missed any log messages using this approach..

http://www.kernel.org/doc/Documentation/networking/netconsole.txt

My commands are :

in the client machine ( which crashes ):

modprobe netconsole netconsole=@/eth0,@128.105.102.217/

where the ip address "128.105.102.217" is the remote machine's ip address. ( which captures logs )

in the remote machine I run the command :

netcat -u -l -p 6666 | tee crashlog

also, iptables --flush helped me remove the udp packet filters which sometimes can filter out the netconsole udp messages.

thanks,
-Leo

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