System Monitor

Hello Every buddy

I'm checking another computer on the network. thats has an stranger 
behavior. Let me explain

This is a Linux/Debian computer installed some 9 days ago. Assigned user 
want to run Moodle on it.
But they called me asking why with 40 users the server went to top 
processor and memory.
Hardware is a Sun-Ultra, with 2GB of RAM, and plenty of scsi disk space...

The problem:
when I run "top" I have between 43% to 52% of processor used by "Sys" 
(System Tasks)
and I cannot identify what is taking these process power.
top does not give anything using the system
nothing is being transfered (checked with iptraf)
no disk usage (using iostat)
no root kits, checked with ckrootkit some minutes ago
no programs listening, checked with netstat

I don't know which tool can help me to find the problem.
I know there should be one and am surfing freshmeat.net, but I can 
happily accept any help you can give

Thanks in advance

Gabriel Orozco

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