LKCD

[Peter M. Petrakis]

Hi,

On 12/21/2010 09:45 AM, Joseph Salisbury wrote:
> Hello,
> 
> I'm attempting to use linux-crashdump to debug an issue.  I've been 
> following the documentation at:
> 
> https://wiki.ubuntu.com/Kernel/CrashdumpRecipe
> 
> The exact steps I've done are:
> Installed linux-crashdump:
> sudo apt-get install linux-crashdump
> Rebooted system to enable crashdump.
> 
> My test to force a crash:
> echo 1 | sudo tee /proc/sys/kernel/panic_on_oops
> echo c | sudo tee /proc/sysrq-trigger
> 
> However, I never get anything in /var/crash.  In fact the /var/crash 
> directory didn't exist until I created it.  I've tried this on Lucid, 
> Maverick and Natty with the same results.
> 
> Has anyone successfully used linux-crashdump recently, or suggest 
> another tool like kdump?  Maybe I'm missing a step?

No that's about right, it should work, but the crashdump package
isn't very robust. Nor is it nearly as configurable as the RHEL
variant, you have to customize it yourself. Judging from the bug
list it doesn't appear to be getting much attention either.

Yes we do use it, and it does work, but it doesn't always work
out of the box. So a few things:

1) I've had issues using kexec in VirtualBox in the past, if you're
trying to sandbox it there, try bare metal instead.

2) Can you do a "simple" kexec and succeed? See the man page on how
to prepare it. Just take what you're booting now, load that, and
kexec. If it works it'll be like a really fast reboot :)

3) kdump *is* linux-crashdump. The old, driver specific method of
dumping is gone. Like diskdump.

4) Not all drivers take kindly to being thrown through kdump/kexec.
Alot of them you don't need. So if you have a serial console, start
taking note of all the peripherals that give you problems, and compile
a new kernel just for the purposes of kdump without those things enabled.

5) kexec/kdump doesn't always work, but with a solid, reproducible test
case, probability will usually grant you with a readable dump :)

> Thanks,
> 
> Joe


Peter