How to Install Nagios no Ubuntu 


Required Packages

Make sure you've installed all the dependencies I have listed below, 

• Apache 2
• PHP 
• GCC compiler and development libraries
• GD development libraries

You can install above dependencies on your Ubuntu by running following commands, 

sudo apt-get install apache2 libapache2-mod-php5 build-essential

Ubuntu 6.10 or earlier versions install the gd2 library using follwoing command,

sudo apt-get install libgd2-dev

Ubuntu 7.10 or later versions install the gd2 library using follwoing command,

sudo apt-get install libgd2-xpm-dev

Nagios account Information

How to become a root user.

sudo -s

Create a new nagios user account and set password.

/usr/sbin/useradd -m -s /bin/bash nagios

passwd nagios

you will need to add a nagios group. No need to follow this step Ubuntu 7.10 or latter versions,

/usr/sbin/groupadd nagios

/usr/sbin/usermod -G nagios nagios

Create a new nagcmd group and add both nagios and apache user,  

/usr/sbin/groupadd nagcmd

/usr/sbin/usermod -a -G nagcmd nagios
/usr/sbin/usermod -a -G nagcmd www-data

Download Nagios 3.2.3 and the Plugins 1.4.15

Create a directory name nagios and downloads

mkdir ~/downloads

cd ~/downloads

wget http://prdownloads.sourceforge.net/sourceforge/nagios/nagios-3.2.3.tar.gz
wget http://prdownloads.sourceforge.net/sourceforge/nagiosplug/nagios-plugins-1.4.15.tar.gz

wget http://sourceforge.net/projects/net-snmp/files/net-snmp/5.7.1/net-snmp-5.7.1.tar.gz/download

Compile and Install Nagios 3.2.3

cd ~/nagios

tar xzf nagios-3.2.3.tar.gz
cd nagios-3.2.3

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

Don't forget to run following commands, 

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

Nagios Server has been installed but Don't start Nagios Server yet. 

Customize Configuration

If you need alerts from Nagios Server put you email address into contacts.cfg
nano /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 Nagios Admin user for login to web interface and set the password up. (don't forget this password)
htpasswd -c /usr/local/nagios/etc/htpasswd.users nagiosadmin

Restar apache server for make changes,
/etc/init.d/apache2 reload

Compile and Install the Nagios Plugins

you must be needed to install net-snmp plugin before install the nagios-plugins-1.4.15,

cd ~/nagios

tar xzf net-snmp-5.7.1.tar.gz

cd net-snmp-5.7.1

./configure

make

make install

cd ~/nagios

tar xzf nagios-plugins-1.4.15.tar.gz
cd nagios-plugins-1.4.15

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

Start Nagios

Configure Nagios to automatically start each and every time the system boots up.
ln -s /etc/init.d/nagios /etc/rcS.d/S99nagios

Verify the sample Nagios configuration files before you start nagios server,

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

Go and start your Nagios server,

sudo /etc/init.d/nagios start

Login to the Web Interface

Here you go, ready to launch by typing following command,
http://localhost/nagios/

Errors and Solutions 

Error 1:
"Externel command error: /usr/local/bin/snmpget: error while loading shared libraries: libnetsnmp.so.30: cannot open shared object file: No such file or directory"
sudo /etc/init.d/nagios restart

Solution1:

Copy libnetsnmp.so.30 file into Ubuntu libraries 

cp /usr/loacl/lib/libnetsnmp.so.30 /usr/lib/libnetsnmp.so.30

Error 2:

"check_mrtgtraf: Unable to open MRTG log file"

Solution 2:

Make sure you set correct .log path into /usr/local/nagios/etc/object/switch.cfg

Each and every command which I have mentioned tested on my Ubuntu 11.10 and it worked for me. 

Hope this help to you...!!!