I was at a linux conference and met someone who sells a tool to patch linux 
kernels live without rebooting.

http://www.kspice.com



Dr Andrew C Aitchison wrote:
> What do other groups do about updating applications and machines
> with long running processes ?
> 
> My users run two sorts of long running processes, with different
> problems when it comes to updates.
> 
> First, I have users who never log off. Thus applications like
> firefox and pdf viewers will be running when they are updated.
> Some time later these applications may try to load and run plugins
> which have been removed/updated.
> 
> Second, I have users with long running calculations (often weeks
> or more) which would be interrupted if the machine were rebooted into an 
> updated kernel. User-writing code often check-points, so the actual 
> calculation time lost is not significant, but calculations in
> commercial packages such as Mathematica and Maple are often less good 
> about check-pointing.
> 
> How do people balance the disruption of killing user processes
> against the need to update to the latest versions of software ?
> 
> Thanks,
>