LKCD

[Joseph Salisbury]

On 12/22/2010 02:21 PM, Peter M. Petrakis wrote:
> 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
>

Thanks for the feedback, Peter.

1) Yes, I've tried bare metal as well as KVM VMs

2) I performed the following kexec, and it did do a really fast reboot :-)

/sbin/kexec --command-line="BOOT_IMAGE=/boot/vmlinuz-2.6.37-11-generic 
root=UUID=16a635bc-7110-4c13-97bf-1a3bb5931a96 ro vt.handoff=7  quiet 
splash irqpoll maxcpus=1 nousb" 
--initrd=/boot/initrd.img-2.6.37-11-generic 
/boot/vmlinuz-2.6.37-11-generic

So seems like kexec is working, but it is not triggered when I do an 
"alt+sysrq c" or "echo c | sudo tee /proc/sysrq-trigger". In either case 
the system just freezes.

3) Thanks for the info about kdump.

4) Thanks for the suggestions, I will try this.

Thanks for the help, Peter!  I appreciate you taking the time, and 
sending me a response.

Joe