Nagios Installation Quick Guide

Introduction

This guide is intended to provide you with simple instructions on how to install Nagios from source (code) on RHEL and have it monitoring your local machine within 20 minutes. No advanced installation options are discussed here – just the basics that will work for almost all users who want to get started. These instructions were written based on a standard RHEL 5 distribution.

What You’ll have

If you follow these instructions, here’s what you’ll end up with:

  • Nagios and the plugins will be installed underneath /usr/local/nagios
  • Nagios will be configured to monitor a few aspects of your local system (CPU load, disk usage, etc.)
  • The Nagios web interface will be accessible at http://localhost/nagios/

Prerequisites

During portions of the installation you’ll need to have root access to your machine.

Make sure you’ve installed the following packages on your RHEL installation before continuing.

  • Apache
  • GCC compiler
  • GD development libraries

You can use yum to install these packages by running the following commands (as root):

	yum install httpd
	yum install gcc
	yum install glibc glibc-common
	yum install gd gd-devel

Create Account Information

Become the root user.

	su -l

Create a new nagios user account and give it a password.

	/usr/sbin/useradd -m nagios
	passwd nagios

Create a new nagcmd group for allowing external commands to be submitted through the web interface. Add both the nagios user and the apache user to the group.

	/usr/sbin/groupadd nagcmd
	/usr/sbin/usermod -a -G nagcmd nagios
	/usr/sbin/usermod -a -G nagcmd apache

Download Nagios and the Plugins

Create a directory for storing the downloads.

	mkdir ~/downloads
	cd ~/downloads

Download the source code tarballs of both Nagios and the Nagios plugins (visit http://www.nagios.org/download/ for links to the latest versions). At the time of writing, the latest versions of Nagios and the Nagios plugins were 3.0.3 and 1.4.11, respectively.

	wget http://osdn.dl.sourceforge.net/sourceforge/nagios/nagios-3.0.5.tar.gz
	wget http://osdn.dl.sourceforge.net/sourceforge/nagiosplug/nagios-plugins-1.4.11.tar.gz

Compile and Install Nagios

Extract the Nagios source code tarball.

	cd ~/downloads
	tar xzf nagios-3.0.5.tar.gz
	cd nagios-3.0.5

Run the Nagios configure script, passing the name of the group you created earlier like so:

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

Compile the Nagios source code.

	make all

Install binaries, init script, sample config files and set permissions on the external command directory.

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

Don’t start Nagios yet – there’s still more that needs to be done…

Customize Configuration

Sample configuration files have now been installed in the /usr/local/nagios/etc directory. These sample files should work fine for getting started with Nagios. You’ll need to make just one change before you proceed…

Edit the /usr/local/nagios/etc/objects/contacts.cfg config file with your favorite editor and change the email address associated with the nagiosadmin contact definition to the address you’d like to use for receiving alerts.

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

Configure the Web Interface

Install the Nagios web config file in the Apache conf.d directory.

	make install-webconf

Create a nagiosadmin account for logging into the Nagios web interface. Remember the password you assign to this account – you’ll need it later.

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

Restart Apache to make the new settings take effect.

	service httpd restart

Note: Consider implementing the ehanced CGI security measures described here to ensure that your web authentication credentials are not compromised.

Compile and Install the Nagios Plugins

Extract the Nagios plugins source code tarball.

	cd ~/downloads
	tar xzf nagios-plugins-1.4.11.tar.gz
	cd nagios-plugins-1.4.11

Compile and install the plugins.

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

Start Nagios

Add Nagios to the list of system services and have it automatically start when the system boots.

	chkconfig --add nagios
	chkconfig nagios on

Verify the sample Nagios configuration files.

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

If there are no errors, start Nagios.

service nagios start

Modify SELinux Settings

Fedora ships with SELinux (Security Enhanced Linux) installed and in Enforcing mode by default. This can result in “Internal Server Error” messages when you attempt to access the Nagios CGIs.

See if SELinux is in Enforcing mode.

	getenforce

Put SELinux into Permissive mode.

	setenforce 0

To make this change permanent, you’ll have to modify the settings in /etc/selinux/config and reboot.

Instead of disabling SELinux or setting it to permissive mode, you can use the following command to run the CGIs under SELinux enforcing/targeted mode:

	chcon -R -t httpd_sys_content_t /usr/local/nagios/sbin/
	chcon -R -t httpd_sys_content_t /usr/local/nagios/share/

For information on running the Nagios CGIs under Enforcing mode with a targeted policy, visit the NagiosCommunity.org wiki at http://www.nagioscommunity.org/wiki.

Login to the Web Interface

You should now be able to access the Nagios web interface at the URL below. You’ll be prompted for the username (nagiosadmin) and password you specified earlier.

http://localhost/nagios/

Click on the “Service Detail” navbar link to see details of what’s being monitored on your local machine. It will take a few minutes for Nagios to check all the services associated with your machine, as the checks are spread out over time.

Other Modifications

Make sure your machine’s firewall rules are configured to allow access to the web server if you want to access the Nagios interface remotely.

Configuring email notifications is out of the scope of this documentation. While Nagios is currently configured to send you email notifications, your system may not yet have a mail program properly installed or configured. Refer to your system documentation, search the web, or look to the NagiosCommunity.org wiki for specific instructions on configuring your system to send email messages to external addresses. More information on notifications can be found here.

Congratulations! You sucessfully installed Nagios. Your journey into monitoring is just beginning.

Be the first to comment

Leave a Reply

Your email address will not be published.


*


CommentLuv badge