How to Install Nagios Monitoring Software on Ubuntu 20.04 LTS
This tutorial exists for these OS versions
- Ubuntu 22.04 (Jammy Jellyfish)
- Ubuntu 20.04 (Focal Fossa)
- Ubuntu 18.04 (Bionic Beaver)
- Ubuntu 16.04 (Xenial Xerus)
- Ubuntu 15.04 (Vivid Vervet)
- Ubuntu 14.04 LTS (Trusty Tahr)
On this page
Nagios is open-source software for system and network monitoring. Nagios can monitor the activity of a host and its services and provides a warning/alert if something bad happens on the server. Nagios can run on Linux operating systems, and we will be using the Ubuntu 20.04 server.
In this tutorial, we will show you step by step installing the Nagios 4.4.x on Ubuntu 20.04. We will install the Nagios Core 4.4.x from source, install the nrpe and nagios plugins, and then add host to monitor to the Nagios server.
Prerequisites
- 2 Ubuntu 20.04 servers
- Nagios server - hostname: nagios20 with an IP: 172.16.0.5
- Ubuntu client - hostname: client01 with an IP: 172.16.0.6
- Root privileges
What we will do:
- Install Packages Dependencies
- Install Nagios Core 4.4.6
- Install Nagios Plugin and NRPE Plugin
- Add Host to Monitor to Nagios Server
- Testing
Step 1 - Install Packages Dependencies
First, we will update the Ubuntu repository and install some packages dependencies for the Nagios installation.
Update the Ubuntu repository using the apt command below.
sudo apt update
After that, install packages dependencies for Nagios installation.
sudo apt install -y autoconf bc gawk dc build-essential gcc libc6 make wget unzip apache2 php libapache2-mod-php libgd-dev libmcrypt-dev make libssl-dev snmp libnet-snmp-perl gettext
And you've installed packages dependencies for Nagios server.
Step 2 - Install Nagios Core 4.4.6
In this step, we will install the latest stable version Nagios Core 4.4.6. And we will install it manually from the source.
- Download Nagios Core 4.4.6
Go to your home directory and download the Nagios Core source code.
cd ~/
wget https://github.com/NagiosEnterprises/nagioscore/archive/nagios-4.4.6.tar.gz
Extract the Nagios package and go to the extracted Nagios directory.
tar -xf nagios-4.4.6.tar.gz
cd nagioscore-*/
- Compile and Install Nagios
First, compile Nagios source code and define the Apache virtual host configuration for Nagios.
sudo ./configure --with-httpd-conf=/etc/apache2/sites-enabled
sudo make all
Create the Nagios user and group, and add the 'www-data' Apache user to the 'nagios' group.
sudo make install-groups-users
sudo usermod -a -G nagios www-data
Install Nagios binaries, service daemon script, and the command mode.
sudo make install
sudo make install-daemoninit
sudo make install-commandmode
After that, install the sample script configuration.
sudo make install-config
Then install the Apache configuration for Nagios and activate the mod_rewrite and mode_cgi modules.
sudo make install-webconf
sudo a2enmod rewrite cgi
Now restart the Apache service.
systemctl restart apache2
And you've installed the Nagios Core 4.4.6.
- Create nagiosadmin user
After installing the Nagios Core, we will add the basic authentication for accessing the Nagios dashboard. And we will be using the basic Apache authentication.
Create a new apache basic authentication for the user the "nagiosadmin".
sudo htpasswd -c /usr/local/nagios/etc/htpasswd.users nagiosadmin
Type your strong password.
And you've created a new user 'nagiosadmin' for the Nagios dashboard authentication.
- Setup UFW Firewall
For the firewall configuration, you will need to add the Apache service and the Nagios server port to the UFW firewall.
Add the SSH and Apache HTTP port using the ufw command below.
for svc in Apache ssh
do
ufw allow $svc
done
Next, start the UFW firewall service and add it to the system boot.
ufw enable
Type 'y' and the UFW firewall service will be activate.
Now check all available rules using the command below.
ufw status numbered
Now you will get both the SSH and Apache services added to the UFW firewall.
And finally, you've completed the Nagios Core installation on the Ubuntu 20.04 server.
Step 3 - Install Nagios Plugins and NRPE Plugin
After installing the Nagios Core, we will install the Nagios Plugins and NRPE Plugins.
Both Nagios and NRPE plugins are available by default on the Ubuntu repository. You can install those packages using the apt command below.
sudo apt install monitoring-plugins nagios-nrpe-plugin
Once the installation is complete, go to the nagios installation directory "/usr/local/nagios/etc" and create a new directory for for storing all server hosts configuration.
cd /usr/local/nagios/etc
mkdir -p /usr/local/nagios/etc/servers
Next, edit the Nagios configuration 'nagios.cfg' using vim editor.
vim nagios.cfg
Uncomment the 'cfg_dir' option that will be used for sotring all server hots configurations.
cfg_dir=/usr/local/nagios/etc/servers
Save and close.
Next edit the configuration file "resource.cfg" and define the path binary files of Nagios Monitoring Plugins.
vim resource.cfg
Define the Nagios Monitoring Plugins path by changing the default configuration as below.
$USER1$=/usr/lib/nagios/plugins
Save and close.
After that, add the nagios admin email contacts by editing the configuration file "objects/contacts.cfg".
vim objects/contacts.cfg
Change the email address with your own.
define contact{
......
email [email protected]
}
Save and close.
Now define the nrpe check command by editing the configuration file "objects/commands.cfg".
vim objects/commands.cfg
Add the following configuration to the end of the line.
define command{
command_name check_nrpe
command_line $USER1$/check_nrpe -H $HOSTADDRESS$ -c $ARG1$
}
Save and close, and the Nagioscore configuration has been completed.
Next, start the Nagios service and add it to the system boot.
systemctl start nagios
systemctl enable nagios
The Nagios service is up and running, check using the following command.
systemctl status nagios
Below is the result.
As a result, the Nagios service is up and running. Now we need to restart the Apache service to apply a new Nagios configuration.
systemctl restart apache2
And the Nagios configuration has been completed.
Open your web browser and type the server IP address following the "nagios" URL path.
http://172.16.0.5/nagios/
Log in with the user "nagiosadmin" and type your password.
And you will get the Nagios Dashboard as below.
As a result, you've installed Nagios on the Ubuntu 20.04 server. And you're able to add hosts to the Nagios server.
Step 5 - Add Linux Host to Monitor
In this step, we will add the Ubuntu server with hostname "client01" and the IP address "172.16.0.6" to the Nagios server.
- Install NRPE Server on the Client01 Server
Log in to the "client01" server using your ssh.
ssh [email protected]
Once you've logged in, update the Ubuntu repository and install Nagios Plugins and NRPE Server.
sudo apt update
sudo apt install nagios-nrpe-server monitoring-plugins
Next, go to the NRPE installation directory "/etc/nagios" and edit the configuration file "nrpe.cfg".
cd /etc/nagios/
vim nrpe.cfg
Uncomment the "server_address" line and change the value with the "client01" IP address.
server_address=172.16.0.6
One the "allowed_hosts" line, add the Nagios Server IP address "172.16.0.5".
allowed_hosts=127.0.0.1,::1,172.16.0.5
Save and close.
Next, edit the "nrpe_local.cfg" configuration.
vim nrpe_local.cfg
Change the IP address with the "client01" IP address, and paste the configuration into it.
command[check_root]=/usr/lib/nagios/plugins/check_disk -w 20% -c 10% -p /
command[check_ping]=/usr/lib/nagios/plugins/check_ping -H 172.16.0.6 -w 100.0,20% -c 500.0,60% -p 5
command[check_ssh]=/usr/lib/nagios/plugins/check_ssh -4 172.16.0.6
command[check_http]=/usr/lib/nagios/plugins/check_http -I 172.16.0.6
command[check_apt]=/usr/lib/nagios/plugins/check_apt
Save and close.
Now restart the NRPE service and add it to the system boot.
systemctl restart nagios-nrpe-server
systemctl enable nagios-nrpe-server
And the Nagios NRPE server is up and running.
Check the NRPE service using the following command.
systemctl status nagios-nrpe-server
The NRPE service is up and running.
Next, back to the Nagios Server and check the "client01" NRPE server.
/usr/lib/nagios/plugins/check_nrpe -H 172.16.0.6
/usr/lib/nagios/plugins/check_nrpe -H 172.16.0.6 -c check_ping
And you will get the result as below.
And you've installed the Nagios NRPE Server and Nagios Plugins on the "client01" host.
- Add Hosts Configuration to the Nagios Server
Back to the Nagios server terminal, go to the "/usr/local/nagios/etc" directory and create a new configuration "server/client01.cfg".
cd /usr/local/nagios/etc
vim servers/client01.cfg
Change the IP address and the hostname with your own and paste the configuration into it.
# Ubuntu Host configuration file1
define host {
use linux-server
host_name client01
alias Ubuntu Host
address 172.16.0.6
register 1
}
define service {
host_name client01
service_description PING
check_command check_nrpe!check_ping
max_check_attempts 2
check_interval 2
retry_interval 2
check_period 24x7
check_freshness 1
contact_groups admins
notification_interval 2
notification_period 24x7
notifications_enabled 1
register 1
}
define service {
host_name client01
service_description Check Users
check_command check_nrpe!check_users
max_check_attempts 2
check_interval 2
retry_interval 2
check_period 24x7
check_freshness 1
contact_groups admins
notification_interval 2
notification_period 24x7
notifications_enabled 1
register 1
}
define service {
host_name client01
service_description Check SSH
check_command check_nrpe!check_ssh
max_check_attempts 2
check_interval 2
retry_interval 2
check_period 24x7
check_freshness 1
contact_groups admins
notification_interval 2
notification_period 24x7
notifications_enabled 1
register 1
}
define service {
host_name client01
service_description Check Root / Disk
check_command check_nrpe!check_root
max_check_attempts 2
check_interval 2
retry_interval 2
check_period 24x7
check_freshness 1
contact_groups admins
notification_interval 2
notification_period 24x7
notifications_enabled 1
register 1
}
define service {
host_name client01
service_description Check APT Update
check_command check_nrpe!check_apt
max_check_attempts 2
check_interval 2
retry_interval 2
check_period 24x7
check_freshness 1
contact_groups admins
notification_interval 2
notification_period 24x7
notifications_enabled 1
register 1
}
define service {
host_name client01
service_description Check HTTP
check_command check_nrpe!check_http
max_check_attempts 2
check_interval 2
retry_interval 2
check_period 24x7
check_freshness 1
contact_groups admins
notification_interval 2
notification_period 24x7
notifications_enabled 1
register 1
}
Save and close.
Now restart the Nagios Server.
systemctl restart nagios
Step 5 - Testing
Back to your browser and wait for some minutes.
Click on the "Hosts" menu and you will get the "client01" has been added.
Below are details monitoring about the "client01" server.
Now you've added Host to monitor to the Nagios Server.
And the installation of Nagios 4.4.6 on Ubuntu 20.04 Server has been completed successfully.
