<div dir="ltr">thank you so much Jerry. That was quite helpful. made me realize that I was getting in way over my head! So now I am reading one of the <a href="https://www.kernel.org/doc/Documentation/kdump/kdump.txt">resources</a>.</div><div class="gmail_extra"><br><div class="gmail_quote">On Thu, Dec 10, 2015 at 6:30 PM, Jerry Snitselaar <span dir="ltr"><<a href="mailto:dev@snitselaar.org" target="_blank">dev@snitselaar.org</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><span class="">On Thu Dec 10 15, Michael Havens wrote:<br>
</span><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><span class="">
I want to see why my kernel panics (if it does) so I was lead to:<br></span>
[1]<a href="https://help.ubuntu.com/lts/serverguide/kernel-crash-dump.html" rel="noreferrer" target="_blank">https://help.ubuntu.com/lts/serverguide/kernel-crash-dump.html</a><span class=""><br>
sudo cat /etc/default/kdump-tools>> USE_KDUMP=1<br>
Will the above line append USE_KDUMP=1 to kdump-tools.<br>
--<br>
:-)~MIKE~(-:<br>
<br></span>
References<br>
<br>
1. <a href="https://help.ubuntu.com/lts/serverguide/kernel-crash-dump.html" rel="noreferrer" target="_blank">https://help.ubuntu.com/lts/serverguide/kernel-crash-dump.html</a><br>
</blockquote>
<br>
I've never played with it on Ubuntu.<br>
<br>
You will need the crashkernel parameter on the boot line so memory<br>
gets set aside to the kdump kernel memory image.<br>
<br>
Also you will need to reboot, so it builds the image if you haven't<br>
already done so (according to that page, Red Hat/Fedora does the same<br>
thing).<br>
<br>
You will probably need to install debug symbols for the kernel in<br>
question. Not sure how that is done for Ubuntu.<br>
<br>
It doesn't look like it explains it on that page, but look to see if<br>
there is a kdump.conf file in /etc, that will probably need to be<br>
modified to suit your system.<br>
<br>
Once you have it up and running, when the system panics it will<br>
jump to the kdump kernel, bring that up, harvest an image of the<br>
memory, then reboot the system and come up again on the regular<br>
kernel.<br>
<br>
Then you would go to /var/crash or wherever it is configured to<br>
place the vmcore file, and then:<br>
<br>
crash /boot/System-map-for-kernel /lib/modules/debug/lib/modules/kernel-rel/vmlinux vmcore<br>
<br>
The vmlinux part would be whatever location it installed the kernel image which still has<br>
debug symbols not stripped.<br>
<br>
Some commands:<br>
<br>
bt - prints backtrace of the current process<br>
bt -a - prints backtrace for processes on all cpus<br>
bt -f - prints the contents of the stack with the backtrace<br>
<br>
help - will list available commands and help command, will print<br>
out detailed help for the commands.<br>
<br>
log - dumps the in memory system log (what you would normally see<br>
with dmesg command)<br>
<br>
set # - set focus to certain pid<br>
set -c # - set focus to certain cpu <br>
dis function-name - provides disassembled code for the function given<br>
<br>
mod - load symbols for a module<br>
<br>
rd - read contents of memory<br>
struct - display a struct, (with address provided as well dumps out<br>
formatted struct with values)<br>
<br>
<br>
Unless you are familiar with kernel internals and assembly code, what<br>
you'll probably want is to:<br>
<br>
set scroll off<br>
log<br>
<br>
And look at the end of the log to find the message where it paniced,<br>
and post those contents somewhere. If it is a distro kernel your best<br>
bet will be contacting those folks.<br>
<br>
Jerry<br>
<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
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</blockquote></div><br><br clear="all"><div><br></div>-- <br><div class="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div><span style="font-size:12.8000001907349px">:-)~MIKE~(-:</span><br></div></div></div></div></div>
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