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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.
What You'll End Up With
If you follow these instructions, here's what you'll end up with:
Distro/OS-Specific Instructions
Naming conventions, commands, directory names, etc. can vary widely across different Linux distros and UNIX variants, so the instructions provided here may have to be altered a bit for your particular situation.
These instructions were written based on a standard Fedora Core 6 Linux distribution.
I have written notes on the differences in installing Nagios on different Linux distributions and other UNIX variants. Click one of the links below to find instructions tailored for your particular operating system or distro.
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.
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:
The Nagios CGIs (web interface) use Boutell's GD library (http://www.boutell.com/gd/) for generating graphics. Most modern distros include this library by default. You can still use Nagios without the GD library, but if you find yourself missing out on the graphics you'll need to install the GD library and recompile/reinstall Nagios.
1) Create Account Information
Become the root user. You may have to use sudo -s on Ubuntu/Debian 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-1.4.7.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
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
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
6) Compile and Install the Nagios Plugins
Extract the Nagios plugins source code tarball.
cd ~/downloads tar xzf nagios-plugins-1.4.7.tar.gz cd nagios-plugins-1.4.7
Compile and install the plugins.
./configure --with-nagios-user=nagios --with-nagios-group=nagios make make install
7) Start Nagios
Add Nagios to the list of system services and have it automatically start when the system boots.
chkconfig --add nagios chconfig 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
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.
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
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.
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.
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...