Adding Linux Host to Nagios Server: A Guide for Dev

Welcome, dear Dev, to this comprehensive guide on adding Linux host to Nagios server. Nagios is a powerful open-source tool for monitoring IT infrastructure, including servers, switches, routers, and more. With Nagios, you can monitor your entire IT environment from a single dashboard and get alerts when something goes wrong. In this article, we’ll walk you through the process of adding a Linux host to Nagios server, step by step.

Part 1: Installing and Configuring Nagios Server

Before we can add a Linux host to Nagios server, we need to have Nagios server up and running. Here are the steps to install and configure Nagios server:

Step 1: Install Required Packages

The first step is to install the required packages on your Nagios server. Depending on your Linux distribution, the commands may vary. Here’s an example for Ubuntu:

Package Name	Description	Command
Apache	Web server	sudo apt-get install apache2
Nagios	Main monitoring software	sudo apt-get install nagios3 nagios-plugins
NRPE	Remote plugin executor	sudo apt-get install nagios-nrpe-server nagios-plugins

Once you have installed the required packages, you need to configure Apache to serve Nagios web interface. Here’s how:

Step 2: Configure Apache

Open the file /etc/apache2/sites-enabled/000-default.conf and add the following lines:

Alias /nagios /usr/local/nagios/shareOptions NoneAllowOverride NoneRequire all grantedOrder allow,denyAllow from all

Restart Apache with the command “sudo service apache2 restart” and you should be able to access Nagios web interface at http://your-server/nagios.

Step 3: Create a Nagios User

To access Nagios web interface, you need to create a Nagios user with the command “sudo htpasswd -c /usr/local/nagios/etc/htpasswd.users nagiosadmin”. Enter a password for the user when prompted.

Step 4: Add Linux Host to Nagios Server Configuration

Now that Nagios server is up and running, we can add a Linux host to its configuration. Here are the steps:

Part 2: Adding Linux Host to Nagios Server

Step 1: Install NRPE Plugin on Linux Host

The first step is to install NRPE plugin on the Linux host you want to monitor. NRPE stands for Nagios Remote Plugin Executor and it allows Nagios server to run plugins on remote hosts. Here’s how to install NRPE plugin on Ubuntu:

sudo apt-get install nagios-nrpe-server nagios-plugins

Once NRPE plugin is installed, you need to configure it to allow Nagios server to execute plugins. Open the file /etc/nagios/nrpe.cfg and add the following line:

allowed_hosts=127.0.0.1,nagios-server-ip

Replace “nagios-server-ip” with the IP address of your Nagios server. Save the file and restart NRPE plugin with the command “sudo service nagios-nrpe-server restart”.

Step 2: Add Linux Host to Nagios Server Configuration

Now we can add the Linux host to Nagios server configuration. Here are the steps:

Step 2.1: Create Host Configuration File

Create a new file /usr/local/nagios/etc/servers/linux-host.cfg with the following contents:

define host {uselinux-serverhost_namelinux-hostaliasLinux Hostaddresslinux-host-ip}

Replace “linux-host” with the hostname of your Linux host and “linux-host-ip” with its IP address. Save the file.

Step 2.2: Create Service Configuration File

Create a new file /usr/local/nagios/etc/services/linux-host.cfg with the following contents:

define service {usegeneric-servicehost_namelinux-hostservice_descriptionCPU Loadcheck_commandcheck_nrpe!check_load}define service {usegeneric-servicehost_namelinux-hostservice_descriptionMemory Usagecheck_commandcheck_nrpe!check_mem}define service {usegeneric-servicehost_namelinux-hostservice_descriptionRoot Partitioncheck_commandcheck_nrpe!check_disk!20%!10%}

This defines three services that Nagios server will monitor on the Linux host: CPU Load, Memory Usage, and Root Partition. You can add more services as needed. Save the file.

Step 3: Verify Nagios Server Configuration

Run the command “sudo /usr/local/nagios/bin/nagios -v /usr/local/nagios/etc/nagios.cfg” to verify the Nagios server configuration. It should report “Total Warnings: 0” and “Total Errors: 0”.

Step 4: Restart Nagios Server

Restart Nagios server with the command “sudo service nagios restart” to apply the new configuration.

Part 3: Conclusion

Congratulations, dear Dev, you have successfully added a Linux host to Nagios server and configured it to monitor CPU Load, Memory Usage, and Root Partition. Nagios is a powerful tool that can help you keep your IT infrastructure running smoothly and avoid downtime. We hope this guide has been helpful to you. If you have any questions or feedback, please refer to the FAQ below or leave a comment.

FAQ

Q1: Can I monitor other services on the Linux host?

Yes, you can add more services to the Linux host configuration file. See the Nagios documentation for a list of available plugins and their commands.

Q2: Can I monitor Windows hosts with Nagios?

Yes, you can install NRPE plugin for Windows and configure it to work with Nagios server. See the Nagios documentation for more information.

Q3: How can I customize Nagios web interface?

You can customize Nagios web interface by modifying the files in /usr/local/nagios/share/ directory. See the Nagios documentation for more information.

Q4: Can I automate Nagios configuration?

Yes, you can use configuration management tools like Puppet or Ansible to automate Nagios configuration. See the documentation for the tool you want to use for more information.

Q5: How can I troubleshoot Nagios server?

You can check the Nagios server logs in /usr/local/nagios/var/nagios.log for any error messages. You can also run Nagios in debug mode with the command “sudo /usr/local/nagios/bin/nagios -d /usr/local/nagios/etc/nagios.cfg” to see more verbose output.