After installing Nagios on our server, the next step is to install the Nagios agent. " Nagios Remote Plugin Executor". With NRPE, Nagios Administrators can use NRPE to monitor Linux servers as it allows you to remotely execute plugins/commands on our Linux machines and get the result back of the executed command.
In this guide, we will install NRPE on our CentOS 7 in order for it to be monitored through a Nagios server.
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Step 1: Install EPEL Repository
The NRPE packages and plugins which will be installed are available under the EPEL yum repository, Enable EPEL repository using one of the below commands.
rpm -Uvh http://dl.fedoraproject.org/pub/epel/7/x86_64/Packages/e/epel-release-7-11.noarch.rpm
Step 2: Install NRPE and NRPE-plugins
Type the commands below to enable the EPEL repository followed by the command below to install NRPE and its plugins.
yum --enablerepo=epel -y install nrpe nagios-plugins
yum install -y nrpe nagios-plugins-all
Step 3: Configure NRPE Add-on
Next, we need to modify the NRPE configuration file to accept connection from the Nagios server by editing the
Add the Nagios servers IP address, separated by comma like below.
Step 4: Configure Nagios Checks
There are some basic attributes and services to monitor on a Linux server which includes the CPU, Memory, Disk, HTTP, FTP, etc. The
/etc/nagios/nrpe.cfg file contains the basic commands to check these attributes and services on remote hosts.
Listed below are some command lines that lets you monitor attributes with the help of Nagios plugins.
Note: The path to Nagios plugins may change depends on your operating system architecture (i386 or x86_64)
command[check_users]=/usr/lib64/nagios/plugins/check_users -w 5 -c 10
command[check_load]=/usr/lib64/nagios/plugins/check_load -w 15,10,5 -c 30,25,20
command[check_root]=/usr/lib64/nagios/plugins/check_disk -w 20% -c 10% -p /dev/mapper/centos-root
command[check_swap]=/usr/lib64/nagios/plugins/check_swap -w 20% -c 10%
command[check_total_procs]=/usr/lib64/nagios/plugins/check_procs -w 150 -c 200
Note: In the above command definition
-w stands for warning and
-c stands for critical.
Step 5: Restart NRPE
After entering the commands, restart the NRPE service:
systemctl start nrpe
systemctl enable nrpe
Step 6 – Test NRPE from Nagios Server
Lastly, login to the Nagios server and execute the following command to verify that Nagios server is able to connect to clients NRPE services.
check_nrpe -H 22.214.171.124
If the connection is successful, it will show a version of clients NRPE package.