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Ben Collins 06-25-2008 12:57 PM

Kernel Crash Dumps
 
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.


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Mario Limonciello 07-01-2008 06:20 AM

Kernel Crash Dumps
 
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?

Regards

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"Daniel J Blueman" 07-01-2008 06:57 AM

Kernel Crash Dumps
 
On Tue, Jul 1, 2008 at 7:20 AM, Mario Limonciello <superm1@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
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Matt Zimmerman 07-23-2008 06:35 PM

Kernel Crash Dumps
 
On Wed, Jun 25, 2008 at 08:57:32AM -0400, 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.

When kexec-tools is installed, it causes my machine to kexec instead of
shutting down or rebooting:

https://bugs.edge.launchpad.net/ubuntu/+source/kexec-tools/+bug/251242

> 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).

This is good news. Given that it doesn't require a special kernel image,
the package should probably be renamed to something more like linux-debug,
since -generic and -server are presumably identical.

> 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.

Further comments on
https://bugs.edge.launchpad.net/ubuntu/+source/apport/+bug/241322

Is there a way to trigger a dump for test purposes? How did you do your
testing?

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Ben Collins 07-26-2008 07:02 PM

Kernel Crash Dumps
 
On Wed, 2008-07-23 at 19:35 +0100, Matt Zimmerman wrote:
> On Wed, Jun 25, 2008 at 08:57:32AM -0400, 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.
>
> When kexec-tools is installed, it causes my machine to kexec instead of
> shutting down or rebooting:
>
> https://bugs.edge.launchpad.net/ubuntu/+source/kexec-tools/+bug/251242

I noticed this as well. I'll upload a fix that defaults to not doing
this.

> > 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).
>
> This is good news. Given that it doesn't require a special kernel image,
> the package should probably be renamed to something more like linux-debug,
> since -generic and -server are presumably identical.

The reason for the debug packages wasn't to boot a different kernel, it
was so that the full -g enabled vmlinux file was available for the
running kernel. This meant possible skew (your running kernel may have
the same ABI, but different version than the debug kernel), so when we
ran makedumpfile to capture the vmcore, it would get things all wrong.

Now we have a vmcoreinfo file included with every kernel (about 6K as
opposed to 60M) which makedumpfile uses to locate the right memory
regions in vmcore, so we don't have to copy all of memory. The still
built debug images are used by developers to process the vmcore+bugs).

The new metapackage definitely should be called just linux-crashdump,
since it isn't specific to any kernel (it just pulls in deps for
makedumpfile, kexec-tools and updated grub).

> > 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.
>
> Further comments on
> https://bugs.edge.launchpad.net/ubuntu/+source/apport/+bug/241322
>
> Is there a way to trigger a dump for test purposes? How did you do your
> testing?

# echo c > /proc/sysrq-trigger


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Brian Murray 03-03-2011 08:46 PM

Kernel Crash Dumps
 
In reviewing the kernel debugging documentation I came across the
instructions for saving a crash dump for a kernel panic[1]. I tried
following them and I'm unable to generate a crash dump. Additionally,
that page hadn't been touched in quite some time. I've also found a bug
report[2] about another person having an issue getting crash dumps.

So my question is - is there something wrong with the documentation?
the crash dump process? or me?


[1] https://wiki.ubuntu.com/Kernel/CrashdumpRecipe
[2] https://bugs.launchpad.net/ubuntu/+source/linux-meta/+bug/710733

Thanks,
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"Peter M. Petrakis" 03-03-2011 09:29 PM

Kernel Crash Dumps
 
On 03/03/2011 04:46 PM, Brian Murray wrote:
> In reviewing the kernel debugging documentation I came across the
> instructions for saving a crash dump for a kernel panic[1]. I tried
> following them and I'm unable to generate a crash dump. Additionally,
> that page hadn't been touched in quite some time. I've also found a bug
> report[2] about another person having an issue getting crash dumps.
>
> So my question is - is there something wrong with the documentation?
> the crash dump process? or me?

It's not you, the system has to be rebooted first. The older
versions of the instructions say to reboot, but the 10.04
ones don't and neither does the "just install this package"
line at the top of the page.

This may have also been fixed in the meantime, I noticed
that /var/crash isn't being created, make sure that exists
after the reboot.

Peter

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Joseph Salisbury 03-03-2011 10:26 PM

Kernel Crash Dumps
 
On 03/03/2011 04:46 PM, Brian Murray wrote:

In reviewing the kernel debugging documentation I came across the
instructions for saving a crash dump for a kernel panic[1]. I tried
following them and I'm unable to generate a crash dump. Additionally,
that page hadn't been touched in quite some time. I've also found a bug
report[2] about another person having an issue getting crash dumps.

So my question is - is there something wrong with the documentation?
the crash dump process? or me?


[1] https://wiki.ubuntu.com/Kernel/CrashdumpRecipe
[2] https://bugs.launchpad.net/ubuntu/+source/linux-meta/+bug/710733

Thanks,



I was able to generate a crash dump on a desktop running Natty.
However, I've been unable to get crash dump to work on a server running
Lucid. Still working on it.


Thanks,

Joe


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Brian Murray 03-03-2011 11:32 PM

Kernel Crash Dumps
 
On Thu, Mar 03, 2011 at 05:29:17PM -0500, Peter M. Petrakis wrote:
>
>
> On 03/03/2011 04:46 PM, Brian Murray wrote:
> > In reviewing the kernel debugging documentation I came across the
> > instructions for saving a crash dump for a kernel panic[1]. I tried
> > following them and I'm unable to generate a crash dump. Additionally,
> > that page hadn't been touched in quite some time. I've also found a bug
> > report[2] about another person having an issue getting crash dumps.
> >
> > So my question is - is there something wrong with the documentation?
> > the crash dump process? or me?
>
> It's not you, the system has to be rebooted first. The older
> versions of the instructions say to reboot, but the 10.04
> ones don't and neither does the "just install this package"
> line at the top of the page.

I rebooted multiple and tested it multiple times.

> This may have also been fixed in the meantime, I noticed
> that /var/crash isn't being created, make sure that exists
> after the reboot.

/var/crash would not exist if you were running a stable release of
Ubuntu as apport crash reporting is turned off then.

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Brian Murray 03-03-2011 11:34 PM

Kernel Crash Dumps
 
On Thu, Mar 03, 2011 at 06:26:18PM -0500, Joseph Salisbury wrote:
> On 03/03/2011 04:46 PM, Brian Murray wrote:
> >In reviewing the kernel debugging documentation I came across the
> >instructions for saving a crash dump for a kernel panic[1]. I tried
> >following them and I'm unable to generate a crash dump. Additionally,
> >that page hadn't been touched in quite some time. I've also found a bug
> >report[2] about another person having an issue getting crash dumps.
> >
> >So my question is - is there something wrong with the documentation?
> >the crash dump process? or me?
> >
> >
> >[1] https://wiki.ubuntu.com/Kernel/CrashdumpRecipe
> >[2] https://bugs.launchpad.net/ubuntu/+source/linux-meta/+bug/710733
> >
> >Thanks,
> >
>
> I was able to generate a crash dump on a desktop running Natty.

How? Your last comment in the bug report mentions intermittent failures
and maxsize is no longer used by apport so that shouldn't have any
effect. I'd really like to get the documentation and or the process
squared away.

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