Re: [Xen-users] Debugging a crash

[Luke S Crawford <lsc@xxxxxxxxx>]

Liam Kirsher <liamk@xxxxxxxxxxx> writes:

> Basically, the whole system just reboots, and there is nothing in any
> of the log files (I've looked in /var/log/messages on host and domUs,
> and on /var/log/xen/xend.log). 

If the Dom0 is panicking, like any other kernel panic, you need either a
logging console or a system dump to see what is happening.  Kdump, I believe,
works with xen, but setting up a serial console is a lot easier and gives
me almost as much useful information.   (at the server janitor level.  I'm 
not really going to look at much more than the backtrace from the kernel 
dump, and that prints to console.  A more skilled programmer might be
able to do more with a dump.) 

Here is a rough-draft of a howto I wrote on setting up serial consoles
(while cabling up my own servers the other weekend)

http://book.xen.prgmr.com/mediawiki/index.php/Serial_console

Essentially I setup a 'buddy system' where each of my servers use com1 
as their console, and then have a null modem from a usb serial dongle to
com1 on a 'buddy server'  -  I then use cu within a logging screen session
to log the output.    Obviously, if I had space in the rack for a serial
concentrator, that would be a superior solution, but I don't, and the 
serial dongles cost me about $3 each on ebay.  


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