This is a beginner-level book, which will introduce Nagios to System Administrators who are interested in monitoring their systems. The focus is on teaching system administrators to secure their systems in a much improved manner incorporating the newer features of Nagios. It will teach Nagios beginners the basics of installation and configuration of version 3; it will show professionals who have already worked on earlier versions of Nagios the new features of Nagios like inheritance and also the new internal functions like better check scheduling. The target readers for this book are System Administrators interested in using Nagios. This book will introduce Nagios with the new features of Version 3 for System Administrators.