Install Nagios Core 4.x

Nagios Server Installation Steps
a. yum install below package

1) httpd
2) php and php-cli
3) gcc
4) glibc and glibc-common
5) gd and gd-devel
6) net-snmp
7) wget

b. vi /etc/httpd/conf/httpd.conf

Change listen port to 8080 (if default 80 had been used)

c. Enable and start httpd services

# systemctl enable httpd
# systemctl start httpd

d. Add Nagios Unix User and Group

# useradd nagios
# passwd nagios (“Nagios”)
# groupadd nagcmd
# usermod –a –G nagcmd nagios
# usermod –a –G nagcmd apache

e. Get Nagios Server Installer file

# wget http://prdownloads.sourceforge.net/sourceforge/nagios/nagios-4.0.8.tar.gz (or latest version)

f. Install with below step

1) # tar xzvf nagios-4.0.8.tar.gz
2) # cd nagios-4.0.8
3) # ./configure --with-command-group=nagcmd
4) # make all
5) # make install
6) # make install-init
7) # make install-config
8) # make install-commadmode
9) # make install-webconf

g. Get latest Nagios Plugins File

# wget http://nagios-plugins.org/download/nagios-plugins-2.0.3.tar.gz

h. Then, install all the plugin

1) # tar xzvf Nagios-plugin-2.0.3.tar.gz
2) # cd Nagios-plugins-2.0.3
3) # ./configure --with-nagios-user=nagios --with-nagios-group=nagcmd
4) # make
5) # make install

i. Create Nagios web access user

# htpasswd -c /usr/local/nagios/etc/htpasswd.users admin
Store the password to be used for web access later

j. Change Directory into Nagios configuration and start configure

# cd /usr/local/nagios/etc/object/
# vi localhost.cfg (server define, add servers and host groups)
# vi commands.cfg (command define, add supported commands)
# vi contacts.cfg (contact define, add alert contact emails)

k. Make sure all file in nagios directory are access by Nagios user

# chown –R nagios:nagcmd /usr/local/nagios

l. Allow apache to read user access file

# chmod 644 /usr/local/nagios/etc/htpasswd.users

m. Enable and start nagios services

# systemctl enable nagios
# systemctl start nagios
(Using port 5666 for Nagios)

2. Testing web access to nagios

a. Start browser and type in Nagios address
http://www.yourdomain.com:8080/nagios.

b. An pop-up menu will display for login, key-in username and password
Username : admin
Password : password

refer to NRPE Installation guide for client Installation and how to use Nagios plugin in client.