Install and Configure Nagios on Debian 11

Switch to Root User

su
    

Disable SELinux (if enabled)

dpkg -l selinux*
    

Install Prerequisite Packages

apt-get update
apt-get install -y autoconf gcc libc6 make wget unzip apache2 apache2-utils php libgd-dev
apt-get install -y openssl libssl-dev
    

Download and Extract Nagios Core

cd /tmp
wget -O nagioscore.tar.gz https://github.com/NagiosEnterprises/nagioscore/archive/nagios-4.4.14.tar.gz
tar xzf nagioscore.tar.gz
    

Compile Nagios Core

cd /tmp/nagioscore-nagios-4.4.14/
./configure --with-httpd-conf=/etc/apache2/sites-enabled
make all
    

Create Nagios User and Group

make install-groups-users
usermod -a -G nagios www-data
    

Install Nagios Binaries

make install
    

Install Nagios Service

make install-daemoninit
    

Install Command Mode

make install-commandmode
    

Install Configuration Files

make install-config
    

Install Apache Config Files

make install-webconf
a2enmod rewrite
a2enmod cgi
    

Configure Firewall for Nagios

iptables -I INPUT -p tcp --destination-port 80 -j ACCEPT
apt-get install -y iptables-persistent
    

Create Nagios Admin User

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

Restart Apache Web Server

systemctl restart apache2.service
    

Start Nagios Service

systemctl start nagios.service
    

Access Nagios Web Interface

Open a web browser and navigate to:

http://your-server-IP/nagios

Log in using:

Username: nagiosadmin
Password: your-password

Once logged in, you should see the Nagios interface.

Install Nagios Plugins

apt-get install -y autoconf gcc libc6 libmcrypt-dev make libssl-dev wget bc gawk dc build-essential snmp libnet-snmp-perl gettext

cd /tmp
wget --no-check-certificate -O nagios-plugins.tar.gz https://github.com/nagios-plugins/nagios-plugins/archive/release-2.4.6.tar.gz
tar zxf nagios-plugins.tar.gz

cd nagios-plugins-release-2.4.6/
./tools/setup
./configure
make
make install
    

Verify Nagios Setup

Revisit the Nagios web interface to ensure proper operation.

Service / Daemon Commands

systemctl start nagios.service
systemctl stop nagios.service
systemctl restart nagios.service
systemctl status nagios.service