For servers or workstations to be responsive and to be kept from being overloaded, it is also worth monitoring system usage using various additional measures. Nagios offers several plugins to monitor resource usage and to report if the limits set for these checks are exceeded.
The first thing that should always be monitored is the system load, and it is calculated based on count of processes running or waiting to run. This value reflects the number of processes and the amount of CPU capacity that they are utilizing. This means that if one process is using up to 50 percent of the CPU capacity, the value will be around 0.5. And if four processes try to utilize the maximum CPU capacity, the value will be around 4.0. The system load is measured in three values: the average loads in the last minute, last 5 minutes, and the last 15 minutes. The syntax of the command is as follows:
check_load [-r] –w wload1,wload5,wload15 –c cload1,cload5,cload15...