Is there any easy way to check this out? Many from my players have dynamic ip numbers so i dont know who is who... I have some annoying players that have multiple accounts and i cannot be sure who is who... I was thinking about .clientinfo member but its seems to not work on linux.. Any ideas?

How I handle problem players - "delete" lol - hehe

That cannot be a rage random ban, it must be sniper shot in one annoying abusing player

There is no easy way
You could log the ip address on logon of all of your players using e.g. the file.em
functions. That can give you a hint of shadow accounts. But you can never be sure cause of the dynamic ip.
But sooner or later it is more than obvious if somebody uses more accounts.
Sometimes they forget to get a new ip.
Nevertheless you have to script this.

If a suspect is online with the same ip you could tell your GM's to check these accounts
by giving them different tasks that they have to solve at the same time. If only one guy/girl controls these account, he/she should have no chance to solve these task. You could script that also

When spotting a shadow account have you done a die roll verses your detect shadow skill?
hehe

doing a whois on an IP block will give you a general location/area/ISP (in a given area).

No scripting required!