How to Install Nagios Core on CentOS Stream 9

Nagios Core, formerly known as Nagios, is a free and open-source computer-software application that monitors systems, networks, and infrastructure. Nagios offers monitoring and alerting services for servers, switches, applications, and services. It alerts users when things go wrong and alert them a second time when the problem has been resolved.

Pre-requisites :

  • A system with CentOS Stream 9 installed and running.

  • root access to the system.

  • LAMP Stack installed and running, for this, you can refer to one of our guides on installing the LAMP Stack (Apache, MariaDB, and PHP).

Once you're all set, we'll proceed with Nagios Core installation and configuration.

Install Wget & Developer Tools

yum groupinstall "Development tools"

yum install wget

Disable SELinux

Next, let us disable SELinux. We are going to set SELinux to permissive. Edit this file:

vi /etc/selinux/config

Then update, Edit this line to permissive:


Install Required Dependencies

Before installing Nagios need to install some required libraries to Nagios Core work properly

yum install -y httpd httpd-tools php gcc glibc glibc-common gd gd-devel make net-snmp

Create Nagios User and Group

useradd nagios
groupadd nagcmd

Next, add both the Nagios and the apache user to the nagcmd group

usermod -G nagcmd nagios
usermod -G nagcmd apache

Download Nagios Core and Nagios Plugin

Check latest version here: Nagios Core Official

Create a directory to install Nagios

mkdir /root/nagios
cd /root/nagios

Command to download Nagios and Nagios plugins


And extract Nagios and its Plugins

tar -xvf nagios-4.4.6.tar.gz
tar -xvf nagios-plugins-2.2.1.tar.gz

Configure Nagios

Enter into Nagios directory

cd nagios-4.4.6/

And run Nagios Configure file

./configure --with-command-group=nagcmd

After configuring, compile and installing required libraries using the make command

make all
make install

In the above output, we can see it listed some libraries to install we can install those using the make install command

for eg,

make install-init
make install-commandmode
make install-config

Remember, these are SAMPLE config files. You'll need to read the documentation for more information on how to define services, hosts, etc. to fit your particular needs.

To get Email alerts configure the file /usr/local/nagios/etc/objects/contacts.cfg

vi /usr/local/nagios/etc/objects/contacts.cfg

NOTE: Replace your Email ID in place of

Install and Configure Web Interface for Nagios

Command to install Web interface

make install-webconf

Command to set a password for the Web interface

htpasswd -s -c /usr/local/nagios/etc/htpasswd.users nagiosadmin

Restart Apache

systemctl start httpd.service

Enable Port 80 & 443

firewall-cmd --zone=public --add-port=80/tcp --permanent
firewall-cmd --zone=public --add-port=443/tcp --permanent
firewall-cmd --reload

Compile and Install Nagios Plugin libraries

Switch to Nagios Plugin

cd /root/nagios
cd nagios-plugins-2.2.1/

And run Nagios Plugin Configuration file

./configure --with-nagios-user=nagios --with-nagios-group=nagios

Next, Compile and Install required libraries

make all
make install

Command to verify Nagios Configuration Files

/usr/local/nagios/bin/nagios -v /usr/local/nagios/etc/nagios.cfg

Enable Nagios Services

systemctl enable nagios
systemctl enable httpd

Login to the Nagios Web Interface

Open a Web browser and enter the following URL to login Nagios Web Interface

NOTE: Replace with your IP address or Fully qualified domain name in place of Your-server-IP-address FQDN




NOTE: Login for the Nagios Web Interface is default Username nagiosadmin and the Password you have set before in the previous step.

Nagios Login

Nagios Web Dashboard

Now you have successfully installed Nagios on CentOS Stream 9.

If you can not configure and face technical difficulties, kindly reach out to us via Support Ticket.