If you are responsible for managing Linux servers or systems, then you must know the importance of monitoring. In order to maintain best uptime, a server often be monitored. You can use either inbuilt tools/commands of linux or can even install third party softwares to monitor and analyze your server. Below, I have listed few commands as well as third party tools that can be used for monitoring purpose. Using these commands, you can analyze disk usage, Disk I/O, Memory/CPU usage, remote monitoring of servers.
Graphical Tools For remote monitoring.
What I meant here by remote monitoring is that the monitoring tool is installed on the remote server and being used to monitor your system so in case your system goes down. Your monitoring system still works and notify you.
It is one of the best and industry leading monitoring tools available out there. It produces various types of grpahs that you can use to monitor your server including disk usage, services on your server memory usage. Many plugins are also available for nagios that you can integrate with it to produce best result. NRPE tools is most useful plugin. It enables you to monitor server remotely.