Initially, Nagios can only monitor remote servers by checking exposed services such as HTTP, FTP, or PostgreSQL. To check items such as CPU, RAM, or disk space, we need to rely on Nagios Remote Plugin Executor (NRPE) to forward system information to the monitoring server upon request. This means that NRPE must be installed on any server we want to monitor, including our PostgreSQL servers.
To install this on Debian-based servers, use the following command:
sudo apt-get install nagios-nrpe-server
Red Hat derivatives will need to use this command:
sudo yum install nrpe
Next, open /etc/nagios/nrpe.cfg and change the allowed_hosts setting to include the IP address or hostname of the monitor server. If 192.168.56.5 is the monitor ...
