Security question with PHP on Unix / Linux.

Hi, I mailed this earlier, but got no response. Maybe it went unnoticed. So, resending it again. Please read below. Your help in this is appreciated. Thanks, Ananth. Hi, I am working on porting PHP onto NetWare. I am newbie to Unix / Linux systems and at this point of time, I am trying to understand the way security is implemented for PHP on Unix / Linux. I mean, how are the different users distinguished from Unix / Linux. Do they get to login into the Unix / Linux system? Do they have separate data space for each user? What is the API that is used to login to Unix / Linux. User may enter his username and password on the browser, but how do they get translated onto the Unix / Linux box? Since I am a newbie, I may have misunderstood some concepts here. Can someone help me in understanding this correctly? Also, can you point me to any documentation on PHP security on Unix systems. I want some in-depth technical stuff upto what calls are made etc. Your help in this is appreciated. Thanks, Ananth.