Server Hang

[Jonathan Billings]

On Fri, May 27, 2011 at 11:20:36AM +1000, Alfredo De Luca wrote:
> Hi all.
> 
> We have Red Hat Enterprise Linux Server release 5.5 running on Sun Blade
> x6270 and occasionally the server hang with just error message in the logs:
> 
> May 23 14:37:41 xxxxxxxxxxxx kernel: SysRq : Resetting

Looks like someone hit the Magic Sysrq key for doing a reset:
http://en.wikipedia.org/wiki/Magic_SysRq_key#Magic_commands
(look at 'b' in the qwerty column)

This is something done either from a keyboard, from a serial console
(if that's set up) or someone running 'echo b > /proc/sysrq-trigger'.  

I think some load-balancing software uses the /proc/sysrq-trigger
method to kill wedged server, so it might be an indicator something
else is resetting the system.


-- 
Jonathan Billings <jsbillin at umich.edu>
College of Engineering - CAEN - Unix and Linux Support