From mboxrd@z Thu Jan  1 00:00:00 1970
From: disnoir <disnoir@gmail.com>
Subject: Re: How could I record the information when kernel panic.
Date: Sat, 27 Apr 2013 12:02:49 +0800
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To: Brandon Philips <brandon@ifup.org>
Cc: linux-newbie@vger.kernel.org

On 04/27/2013 01:33 AM, Brandon Philips wrote:
> On Wed, Apr 24, 2013 at 10:18 AM, disnoir<disnoir@gmail.com>  wrote:
>> So, How could I record the kernel error/info, when system was halt ?
> Your best bet is to use one of the following:
> 0) Use sysrq to investigate a bit:
> https://www.kernel.org/doc/Documentation/sysrq.txt
> 1) Hook a serial console up if your system has one to another system
> with a null modem cable and console=ttyS0,<baud>  passed in to the
> kernel at boot
> 2) Try netconsole if you don't have a serial console:
> https://www.kernel.org/doc/Documentation/networking/netconsole.txt
>
> I would recommend trying a newer kernel and see if your bug is fixed.
> If it is you could bisect down to the commit that fixes it and let the
> debian kernel maintainers know.
>
> Good luck,
>
> Brandon
Thank you for your reply.
I use ttyUSB0 to record the dmesg, cause this is a notebook 
(asus-k42je), which has no serial port, so I use a 
serial-port-to-USB-convertor.
I found that if I add console=ttyUSB0,115200n8 to kernel parameter, the 
kernel will fail to boot, and also without any information.
so I get into system on normal configuration (without console=...), and 
modify rsyslog.conf to log kernel info to /dev/ttyUSB0.
That works, use another pc to watch that serial port, all the 
information in dmesg will show in that serial port either.
But, when I test that if will also work during the kernel-panic ( I try 
"echo c > /proc/sysrq-trigger" ), nothing record into serial.
I guess kernel crash will cause rsyslogd no working.
So I use kdump-tools, kexec-tools to record a kernel dump, and this 
could work even on kernel-panic.
Now, I just need to wait the problem happen again.

:-)

disnoir
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