[K12OSN] cron to kill users or group?

[Mike Ely]

William Fragakis wrote:
> Hi,
> An issue we frequently have is that repeated instances of programs 
> orphaned eventually bring down a server. It arises from a couple of 
> situations: 1) a client crashing then gets rebooted or 2) multiple 
> instances of a program are opened (eg TuxPaint) instead of using an 
> already open program. The second type is the more difficult because we 
> have a lot of young kids and in a special situation, special needs kids 
> - so we want something transparent to them. We'd rather sort the problem 
> out on the server side than "educate" them since exploring the computer 
> is so much fun for them. I've found scripts that kill a certain user, 
> I've found scripts that kill certain processes but what I'd like is 
> something that ends all the regular user processes, say, at midnight and 
> let's the clients "refresh" without having to reboot or log back in. I 
> don't want to restart the server every night - well, because it's a 
> server and we love our uptime.
> 
> Is anyone using anything to end the processes for a certain group, say, 
> as a cron job?
> 
> TIAA
> William Fragakis
> Morris Brandon Elementary
>

Yes, there is - the program is called "slay" and it's actually a pretty 
simple shell script.  With Debian, just apt-get install slay, and I'm 
guessing redhat will have it in a yum repository.

As far as getting it into cron, it's just a matter of slaying by 
username with whatever signal you want to pass the processes:
usage: slay [-signal] name [name...]
        Kills all processes belonging to any of the given names.
        Use -clean as a signal name to kill with TERM first and then 
with KILL.

I once wrote a program called "slayer" to keep generic student accounts 
off my LTSP lab (because Firefox and OpenOffice don't like multiple 
instances with the same user account) - it went something like this:

	#!/bin/sh
	while true; do
	sleep 10s
	slay <generic account usernames>
	done

Heavy metal references aside, I'm sure you could get something similar 
into your crontab without much difficulty.

Cheers,
Mike