How to Install and Configure Nagios in CentOS

How to Install and Configure Nagios in CentOS

Today, We will learn How to Install and Configure Nagios in CentOS. Nagios is best monitoring tools and nagios offers monitoring and alerting for servers, switches, application, and services. It alerts users when things go wrong and alerts them again when the problem has been resolved. Let’s start installation of nagios :

 Nagios XI – Hardware Requirements

Supported Distributions

Nagios XI is currently supported with the following Linux distributions for both 32 and 64 bit installations:

CentOS 5/6

RHEL 5/6

 Server requirement for nagios

Fresh Running Linux server that has network access and a C compiler installed. You will need to have the following software installed.

1. A web server (preferrably Apache)
2. gd library version 1.6.3 or higher

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 will need to have root access to your machine. Make sure you’ve installed the following packages on your OS installation before continuing.

• Apache
• PHP
• GCC Compiler
• GD Development Libraries

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

yum install httpd php

yum install gcc glibc glibc-common

yum install gd gd-devel

After Confirm all above things then you can start the process for installation of nagios

First we will create user for nagios :

1] 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 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

After user and group create then you need to download the nagios script.

2] Download Nagios and the plugins

Create a directory for storing the download.

mkdir ~/downloads

cd ~/downloads

Download the source code tarballs of both Nagios and the Nagios plugins (visit http://www.nagios.org/download links and download the latest version of nagios). These directions were tested with nagios-3.4.2 and Nagios Plugins 1.4.16.

After download the both application we will start to install it

3] Compile and Install Nagios

Extract the Nagios source code tarball.

cd ~/downloads

tar –xzf nagios-3.x.x.tar.gz

cd nagios-3.x.x

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

./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 because of there is still more that needs to be done…

4] 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 alearts.

vi /usr/local/nagios/etc/object/contacts.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 because of you will need it later.

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

OR

If htpasswd command is not working then use below step for htpasswd :

cd /usr/local/apache/bin

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

Restart apache to make the new setting take effect.

/etc/init.d/service httpd restart

OR

service httpd restart

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

6] Compile and install the Nagios Plugins

Extract the nagios plugins source code tarball.

cd ~/downloads

tar xzf nagios-plugins-1.x.x.tar.gz

cd nagios-plugins-1.x.x

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

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

8] Modifiy SELinux Settings :

Centos with SELinux installed and in Enforcing mode by default. Thins 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 will 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

9] Login to the Web Interface :

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

http://localhost/nagios/

click on the “service details” navbar link to see details of What’s being monitored on your local machine.