Kernel Crash Dumps

[Daniel J Blueman]

On Tue, Jul 1, 2008 at 7:20 AM, Mario Limonciello <superm1 at ubuntu.com> wrote:
> Ben Collins wrote:
>> As of the last kernel upload in intrepid, we now have the ability to
>> automatically capture crash dumps from kernel panics.
>>
>> To enable this, you can install the linux-crashdump-generic meta
>> package. If you don't have universe in your repo, you will also need to
>> get the makedumpfile package.
>>
>> Once you reboot, everything will be enabled. Any panic by the kernel
>> will reboot into the crashkernel, and save away the kernel core
>> to /var/crash/vmcore.
>>
>> Right now, this requires a linux-image-debug-generic package (pulled in
>> by the crashdump meta package). However, with the next kernel upload,
>> this wont be needed (saves you from installing a 50Meg package).
>>
>> Apport has a bug filed so that it will detect these vmcore's and handle
>> them appropriately by asking the user to file a bug with the vmcore
>> attached.
>>
>>
>>
> Ben:
>
> It's great to see this fully enabled now.  Will there be any
> disadvantages to having all of this running at all times?  Is the
> eventual goal going to be to boot into this type of "crash ready" mode
> for everyone, or just when someone has a reproducible panic they will be
> recommended to install this crashdump meta?

Just to add my experience - the disadvantages are:

 - 64/128MB memory is always reserved (no problem actually)
 - dumps in /var/crash starts eating up your disk (not a problem
unless you're a developer)
 - it can be confusing when the system automatically boots (in order
to write the dump) then reboots
 - any graphical VGA console isn't reset at kexec time, so you don't
see what's happening in this case

In practise, these are really minor points. As long as we educate the
user with the right message/warning when the dump-kernel is booted,
they'll have the patience to not press reset (or something) when gdm
doesn't start. Also, a cron script delete old dumps is handy.

Daniel
-- 
Daniel J Blueman