Nagios

Quickstart Installation Guide


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See Also: Upgrading Nagios, Configuration Overview

Introduction

This guide is intended to provide you with simple instructions on how to install Nagios from source (code) and have it monitoring your local machine inside of 20 minutes. No advanced installation options are discussed here - just the basics that will work for 95% of users who want to get started.

Note: These instructions were written based on a standard Fedora Core 6 Linux distribution. Naming conventions, commands, etc. vary across different Linux distros and UNIX variants, so the instructions provided here may have to be altered a bit for your situation. If you're having trouble using these instructions, you can find OS/distribution-specific installation guides, HOWTOs, and other helpful installation documentation on the NagiosCommunity.org wiki.

What You'll End Up With

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

Prerequisites

During portions of the installation you'll need to have root access to your machine. You'll also need the following items installed before you can proceed:

You can still install and use Nagios without the GD library if you need to, as it is only used by a few of the CGIs for generating graphics. Let's get started!

1) Create Account Information

Become the root user. You may have to use sudo -s on Ubuntu and other distros.

su -l

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

/usr/sbin/useradd 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. Ubuntu and other distros may require www-data or httpd to be used instead of apache. Use the name of the account that your web server runs under.

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

2) 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).

wget http://osdn.dl.sourceforge.net/sourceforge/nagios/nagios-3.0a2.tar.gz
wget http://osdn.dl.sourceforge.net/sourceforge/nagiosplug/nagios-plugins-1.4.6.tar.gz

3) Compile and Install Nagios

Extract the Nagios source code tarball.

cd ~/downloads
tar xzf nagios-3.0a2.tar.gz
cd nagios-3.0a2

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

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

chkconfig --add nagios
chconfig nagios on

Don't start Nagios yet - there's still more that needs to be done...

4) Customize Configuration

Edit the localhost.cfg config file 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/localhost.cfg

5) Configure the Web Interface

Copy the sample web config file to the Apache conf.d directory.

cp sample-config/httpd.conf /etc/httpd/conf.d/nagios.conf

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

6) Compile and Install the Nagios Plugins

Extract the Nagios plugins source code tarball.

cd ~/downloads
tar xzf nagios-plugins-1.4.6.tar.gz
cd nagios-plugins-1.4.6

Compile and install the plugins.

./configure
make
make install

The permissions on the plugins will need to be fixed at this point (I believe this is a bug with the plugin distribution), so run the following commands in order.

chown nagios /usr/local/nagios/libexec/*
chown root.nagios /usr/local/nagios/libexec/check_dhcp
chown root.nagios /usr/local/nagios/libexec/check_icmp
chmod 4550 /usr/local/nagios/libexec/check_dhcp
chmod 4550 /usr/local/nagios/libexec/check_icmp

7) Start Nagios

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

8) 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.

Note: If you get "Internal Server Error" error messages while attempting to view the CGIs, it's likely due to the fact that SELinux is installed and enabled on your system. See below for information on fixing this.

9) Modify SELinux Settings

If you don't get any errors when access the CGIs, you can skip this step. 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

The Nagios CGIs should work now. To make this change permanent, you'll have to modify /etc/selinux/config. 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.

10) 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.

11) You're Done

Congratulations! You sucessfully installed Nagios. Your journey into monitoring is just beginning. You'll no doubt want to monitor more than just your local machine, so check out the following docs...