krish – 起死回生 [Wake up from death & return to life.]

December 8, 2012

Right Now: What am I up to?

Dec 08, 2012. 02:03 am IST – A new logo coming up for Toonheart.


Finalising the logo for my gaming startup - Toonheart  :)Dealing with hand sprain but it can't be helped.... Work is Work.

Finalising the logo for my gaming startup – Toonheart 🙂
Dealing with sprained wrist, but it can’t be helped…. Work is Work.

Nov 18, 2012. 01:41 am IST – Still working on my prototype game.

Fighting 13C weather off with my biking balaclava,

Indie Game Dev’s Life.

and listening to this in loop mode.

To read my past time entries click on (more…)

September 28, 2011

Core dump Xen domU/guests

Filed under: Free / Open Source — krish @ 7:39 pm
Tags: , , , , , , , , , , ,

If you’ve been wondering why on_crash='coredump-restart' or on_crash='coredump_restart'(as per some manuals) doesnt work or gives you
“Error: Invalid event handling mode: crash”, here’s why:

I spend hours looking for the answer, and no one one ##xen would also tell me why (asked multiple times, and idled long enough)..and after breaking my head for hours I found the answer.
So listen carefully 🙂

A. Xendump can be configured to capture vmcore dumps of para-virtualized (PV) Xen domU/guests automatically upon a crash. ie., by using on_crash=’coredump-restart’

B. Core dumps from fully-virtualized (FV) Xen domU/guests can only be taken manually by running the `xm dump-core` command.


Here’s a detailed how-to on enabling coredump for Xen domU/guest:


1. On the dom0/Xenserver, edit /etc/xen/xend_config.sxp and uncomment
# (enable-dump no)
and make it
(enable-dump yes)

2. Restart Xend (depending on whether you use init.d scripts or service utility)
# /etc/init.d/xend restart
# service xend restart

3. On the domU/Guest, edit domU.cfg (domU’s configuration file) and add/edit line

#If your domU is fully-virtualized


#If your domU is para-virtualized

4. Start domU

# xm create /path/to/domU.cfg

5. Now, if your domU/guest is para-virtualized, login to the domU and

Check if kernel.panic key is true
# sysctl -A | grep -e kernel | grep -e panic

Set them if they are not
# sysctl -w kernel.panic=1
# sysctl -w kernel.panic_on_oops=1

6. Test it from inside domU/Guest. (Para-Virtualized Guest)
Warning: The next line of code will crash your domU for test.

# echo "c" >/proc/sysrq-trigger

Note: The above command is a way of invoking magic sysrq
a. It will not work if sysrq is disabled on the box
b. NO. I am not gonna talk about magic sysrq’s in this post; or even how to find if its disabled 🙂

7. Test it from dom0/Xenserver. (Fully-Virtualized Guest)
Warning: The next line of code will crash your domU for test.

# xm dump-core -C

8. Above steps 6/7 will dump vmcore to /var/xen/dump (default directory unless you have changed it)
Oh, BTW, make sure you create that directory if it doesn’t exists before taking the dump 😀

Enjoy analyzing the dump 😉

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