Monitoring resources

For servers or work stations 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.

Checking system load

The first thing that should always be monitored is the system load, and it is calculated based on the count of the processes running or waiting to be running. 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% 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 last 15 minutes. The syntax of the command and the description of the option is as follows:

check_load [-r] -w wload1,wload5,wload15...