Nagios is Invasive?

Hi, I have to check if some services or if some server of my customers are up and running from one of my server.
Does NAGIOS can help me without installing add on or something similar to the server of my customers???

Where I can find some documents about nagios??
THX

nagios Docs is avaiable at
http://www.nagios.org/docs/
Edited Fri Dec 17 2004, 01:56AM ]

If the service you are interested in on the “customer’s” server is available through snmp, then no, you don’t need to install anything. Also, the ftp checks, http checks, sql checks, and many others, are not invasive. They can be configured to actually login to an ftp server, though, which is a darn good sign that the ftp server is running. Is that invasive? Perhaps to some, yes, but how else are you going to know if it’s up?