The Linux monitoring systems are often used to follow system resources, such as CPU load, the amount of free RAM, network traffic statics or memory consumption. Which are ones from the most important tasks for every administrators. Furthermore, those tools notify the network administrator (via email, SMS or other alarms) when something interrupts or goes down which makes their life easier.

From those monitoring tools we will list the 7 most important in this article which will be described and identified by giving their features and mentioning their current version.

Full article here:
List of Free And Open Source Monitoring System (Unixmen)