The important aspect of graphing is that it enables a busy administrator to evaluate a server visually, often making more sense than strings of data. NagiosGrapher is a tool that you can use with Nagios to graph information that you want to evaluate as an administrator. This tutorial will show you how to install Nagiosgrapher in preparation for the data to be graphed.

RedHat based systems (rhel/fedora/centos) use rpm/yum to install and upgrade packages. If the rpm database gets corrupted in some way it will break all the functionality of rpm and other tools that rely on it like yum for example.
This post will show how to rebuild your rpm database and bring back to life your rpm command.

What is CentOS?
CentOS is an Enterprise Linux distribution based on the freely available sources from Red Hat Enterprise Linux. Each CentOS version is supported for 7 years (by means of security updates). A new CentOS version is released every 2 years and each CentOS version is regularly updated (every 6 months) to support newer hardware. This results in a secure, low-maintenance, reliable, predictable and reproducible Linux environment.