Please follow the steps to install nagios. 

Download nagios from source 

wget http://prdownloads.sourceforge.net/nagios/nagios-2.9.tar.gz?download

Unpack the sourc file 

tar -xzvf nagios-2.9.tar.gz

create user for nagios

useradd nagios

 Create Installation Directory

mkdir /usr/local/nagios

Change the owner of the base installtion directory to be the Nagios user and group you added earlier as follows:

chown nagios.nagios /usr/local/nagios

 Create a new command file group whose members include the user your web server is running as and the user Nagios is running
as.

groupadd nagcmd 

 Add the users that your web server and Nagios run as to the newly created group

usermod -G nagcmd nagios
usermod -G nagcmd nobody

 Run the configuration script.

./configure –prefix=/usr/local/nagios –with-cgiurl=/nagios/cgi-bin –with-htmurl=/nagios/ –with-nagios-user=nagios –with-nagios-group=nagios –with-command-group=nagcmd

 Compile Binaries-

make all

 Install the Binaries And HTML Files-

make install 

9. Install An Init Script-

make install-init

 Download Nagios plugin to /usr/local/nagios  from

wget http://downloads.sourceforge.net/nagiosplug/nagios-plugins-1.4.9.tar.gz?modtime=1180952247&big_mirror=0

untar; and cd into the new directory.

 Compile Binaries- make

 make install

 Setup The Web Interface

ADD THE FOLLOWING ENTRIES TO HTTPD.CONF

Configure Aliases and Directory Options For The Web Interface

ScriptAlias /nagios/cgi-bin/ /usr/local/nagios/sbin/
<Directory /usr/local/nagios/sbin/>
AllowOverride AuthConfig
Options ExecCGI
Allow from all
Order allow,deny
</Directory>

Alias /nagios/ /usr/local/nagios/share/
<Directory /usr/local/nagios/share>
Options None
AllowOverride AuthConfig
Order allow,deny
Allow from all
</Directory>

 Include the file in the Apache configuration file.

 Create a user for the web authentication -nagiosadmin
 Provide a password that will be used when nagiosadmin authenticates to the web server.

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

 Enable Authentication/Authorization Functionality In The CGIs

Set use_authentication=0 in cgi.cfg file.

Set the default Permissions To CGI Information

authorized_for_system_information=nagiosadmin
authorized_for_configuration_information=nagiosadmin
authorized_for_system_commands=nagiosadmin
authorized_for_all_services=nagiosadmin
authorized_for_all_hosts=nagiosadmin
authorized_for_all_service_commands=nagiosadmin
authorized_for_all_host_commands=nagiosadmin

  Restart The Web Server

 cd  /user/local/nagios/etc

  Create directories hosts and services

mkdir hosts.
mkdir services.

  Specify the directories in the nagios.cfg file.

cfg_dir=/usr/local/nagios/etc/hosts
cfg_dir=/usr/local/nagios/etc/services

 In each of these directories we need to create files for each servers we need to monitor.
Each of these files will contain the hostname and ip of the respective servers.
For this we need to make a copy of the HOSTS block in the localhost.cfg file for each servers.
Similarly we need to make a copy of the SERVICES block of the localhost.cfg for each servers
in the services directory.

  We need to specify the emailID where we recieve the alerts in the localhost.cfg file.

 Also we need to add all the hostname we are monitoring in the HOSTGROUP of the localhost.cfg file.

 Once this is done, we need to start nagios.

We can see the logg details of nagios in the /usr/local/nagios/var/nagios. log file.

This completes the configuration of NAGIOS!!!

SAMPLE CONFIGURATION TO ADD A HOST
———————————-

# Generic host definition template – This is NOT a real host, just a template!

define host{
        name                            generic-host    ; The name of this host template
        notifications_enabled           1               ; Host notifications are enabled
        event_handler_enabled           1               ; Host event handler is enabled
        flap_detection_enabled          1               ; Flap detection is enabled
        failure_prediction_enabled      1               ; Failure prediction is enabled
        process_perf_data               1               ; Process performance data
        retain_status_information       1               ; Retain status information across program restarts
        retain_nonstatus_information    1               ; Retain non-status information across program restarts
        notification_period             24×7            ; Send host notifications at any time
        register                        0               ; DONT REGISTER THIS DEFINITION – ITS NOT A REAL HOST, JUST A TEMPLATE!
        }

# Linux host definition template – This is NOT a real host, just a template!

define host{
        name                            swww3.couchsurfing.com  ; The name of this host template
        use                             generic-host    ; This template inherits other values from the generic-host template
        check_period                    24×7            ; By default, Linux hosts are checked round the clock
        max_check_attempts              10              ; Check each Linux host 10 times (max)
        check_command                   check-host-alive ; Default command to check Linux hosts
        notification_period             workhours       ; Linux admins hate to be woken up, so we only notify during the day
                                                        ; Note that the notification_period variable is being overridden from                                                        ; the value that is inherited from the generic-host template!
        notification_interval           120             ; Resend notification every 2 hours
        notification_options            d,u,r           ; Only send notifications for specific host states
        contact_groups                  admins          ; Notifications get sent to the admins by default
        register                        0               ; DONT REGISTER THIS DEFINITION – ITS NOT A REAL HOST, JUST A TEMPLATE!
        }

# Since this is a simple configuration file, we only monitor one host – the
# local host (this machine).

define host{
        use                     swww3.couchsurfing.com           ; Name of host template to use
                                                        ; This host definition will inherit all variables that are defined
                                                        ; in (or inherited by) the linux-server host template definition.
        host_name               swww3.couchsurfing.com
        alias                   swww3.couchsurfing.com
        address                 207.210.80.122
}

SAMPLE CONFIGURATION TO ADD SERVICES TO A HOST
———————————————-

# Generic service definition template – This is NOT a real service, just a template!

define service{
        name                            generic-service         ; The ‘name’ of this service template
        active_checks_enabled           1                       ; Active service checks are enabled
        passive_checks_enabled          1                       ; Passive service checks are enabled/accepted
        parallelize_check               1                       ; Active service checks should be parallelized (disabling this can lead to major performance problems)
        obsess_over_service             1                       ; We should obsess over this service (if necessary)
        check_freshness                 0                       ; Default is to NOT check service ‘freshness’
        notifications_enabled           1                       ; Service notifications are enabled
        event_handler_enabled           1                       ; Service event handler is enabled
        flap_detection_enabled          1                       ; Flap detection is enabled
        failure_prediction_enabled      1                       ; Failure prediction is enabled
        process_perf_data               1                       ; Process performance data
        retain_status_information       1                       ; Retain status information across program restarts
        retain_nonstatus_information    1                       ; Retain non-status information across program restarts
        is_volatile                     0                       ; The service is not volatile
        register                        0                       ; DONT REGISTER THIS DEFINITION – ITS NOT A REAL SERVICE, JUST A TEMPLATE!
        }

# Local service definition template – This is NOT a real service, just a template!

define service{
        name                            local-service           ; The name of this service template
        use                             generic-service         ; Inherit default values from the generic-service definition
        check_period                    24×7                    ; The service can be checked at any time of the day
        max_check_attempts              4                       ; Re-check the service up to 4 times in order to determine its final (hard) state
        normal_check_interval           5                       ; Check the service every 5 minutes under normal conditions
        retry_check_interval            1                       ; Re-check the service every minute until a hard state can be determined
        contact_groups                  admins                  ; Notifications get sent out to everyone in the ‘admins’ group
        notification_options            w,u,c,r                 ; Send notifications about warning, unknown, critical, and recovery events
        notification_interval           60                      ; Re-notify about service problems every hour
        notification_period             24×7                    ; Notifications can be sent out at any time
        register                        0                       ; DONT REGISTER THIS DEFINITION – ITS NOT A REAL SERVICE, JUST A TEMPLATE!
        }

# Define a service to “ping” the local machine

define service{
        use                             local-service         ; Name of service template to use
        host_name                       www4.couchsurfing.com
        service_description             PING
        check_command                   check_ping!100.0,20%!500.0,60%
        }

# Define a service to check the disk space of the root partition
# on the local machine.  Warning if < 20% free, critical if
# < 10% free space on partition.

define service{
        use                             local-service         ; Name of service template to use
        host_name                        www4.couchsurfing.com
        service_description             Root Partition
        check_command                   check_local_disk!20%!10%!/
        }

# Define a service to check the number of currently logged in
# users on the local machine.  Warning if > 20 users, critical
# if > 50 users.

define service{
        use                             local-service         ; Name of service template to use
        host_name                        www4.couchsurfing.com
        service_description             Current Users
        check_command                   check_local_users!20!50
        }

# Define a service to check the number of currently running procs
# on the local machine.  Warning if > 250 processes, critical if
# > 400 users.

define service{
        use                             local-service         ; Name of service template to use
        host_name                        www4.couchsurfing.com
        service_description             Total Processes
        check_command                   check_local_procs!250!400!RSZDT
        }

# Define a service to check the load on the local machine.

define service{
        use                             local-service         ; Name of service template to use
        host_name                        www4.couchsurfing.com
        service_description             Current Load
        check_command                   check_local_load!5.0,4.0,3.0!10.0,6.0,4.0
        }

Requirements:

Mysql
Php
Rrdtool
net-snmp
net-snmp-devel.i386
net-snmp-libs.i386
net-snmp-perl.i386
net-snmp-utils.i386
php-snmp
Apache with PHP Support

MySQL configuration for cacti:

mysql -u root -p
mysql> create database cacti;
mysql> grant all on cacti.* to cactiuser@’localhost’ identified by ‘cactipassword’;
mysql> flush privileges;

RRDTool Installation

Requirements:

tcl
tcl-devel

[root]# cd /usr/local/src/
[root]# wget http://oss.oetiker.ch/rrdtool/pub/rrdtool.tar.gz
[root]# tar -zxf rrdtool.tar.gz
[root]# cd rrdtool*
[root]# ./configure
[root]# make
[root]# make install
[root]# make site-perl-install

                  OR

 yum install -y rrdtool*

[root]# useradd cactiuser
[root]# tar -zxvf cacti*
[root]# mv cacti-0.8.xx /home/cactiuser/cacti
[root]# cd /home/cactiuser/cacti
[root]# mysql cactidb < cacti.sql

Edit config.php:

[root]# vi /include/config.php
$database_defaut = “cacti”;
$database_hostname = “localhost”;
$database_username = “cactiuser”;
$database_password = “cactipassword”

Adding CRON Job:

[root]# crontab -e
*/5 * * * * cactiuser php /home/cactiuser/cacti/poller.php > /dev/null 2>&1

In httpd.conf:

Alias /cacti/ “/home/cactiuser/cacti/”

Restart Services 

/etc/init.d/httpd restart
/etc/init.d/mysqld restart

Cacti Installed Successfully…
Access: http://localhost/cacti
Login with username/password : admin/admin