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is a powerful monitoring system that enables you to identify and
resolve infrastructure problems before they affect critical

Designed with scalability and
flexibility in mind, Nagios gives you the peace of mind that comes
from knowing your business processes won’t be affected
by unknown outages.

Nagios is a powerful tool that
provides you with instant awareness of your organization’s
mission-critical IT infrastructure. It allows you to detect and
repair problems and mitigate future issues before they affect
end-users and customers.

By using Nagios, you can:

  • Plan
    for infrastructure upgrades before outdated systems cause failures
  • Respond
    to issues at the first sign of a problem
  • Automatically
    fix problems when they are detected
  • Coordinate
    technical team responses
  • Ensure
    your organization’s SLAs are being met
  • Ensure
    IT infrastructure outages have a minimal effect on your
    organization’s bottom line
  • Monitor
    your entire infrastructure and business processes 
    To use Nagios, first make the necessary alterations to your network configuration file. 

# vi /etc/sysconfig/network-scripts/ifcfg-eth0

Add the following to the configuration file, fill the X’s to your
IP configuration:


Save and close the file, then restart the network

# service network restart
Now install the nagios related packages

# yum install httpd php gcc glibc glibc-common gd gd-devel openssl-devel wget perl make
Create the nagios user and set the password

# /usr/sbin/useradd -m nagios
# passwd nagios

Create the nagios group, nagcmd, which will allow external commands to be submitted through the web interface. 
Then add the nagios user and apache user to the group
# /usr/sbin/groupadd nagcmd

# /usr/sbin/usermod -a -G nagcmd nagios

# /usr/sbin/usermod -a -G nagcmd apache
Create a temp directory to place
the nagios downloads
# mkdir ~/downloads

cd ~/downloads

Download nagios

# wget http://prdownloads.sourceforge.net/sourceforge/nagios/nagios-3.5.0.tar.gz  
Extract the nagios tar ball

# cd nagios
Run the nagios script passing the nagcmd group

# ./configure --with-command-group=nagcmd

General Options:
Nagios executable: nagios
Nagios user/group: nagios,nagios
Command user/group: nagios,nagcmd
Embedded Perl: no
Event Broker: yes
Install ${prefix}: /usr/local/nagios
Lock file: ${prefix}/var/nagios.lock
Check result directory: ${prefix}/var/spool/checkresults
Init directory: /etc/rc.d/init.d
Apache conf.d directory: /etc/httpd/conf.d
Mail program: /bin/mail
Host OS: linux-gnu

Web Interface Options:
HTML URL: http://localhost/nagios/
CGI URL: http://localhost/nagios/cgi-bin/

Compile the nagios source code
# make all
Install the binaries, init script, sample configs, and set
permissions on external command directory

# make install

# make install-init

# make install-config

# make install-commandmode

The sample config files have been installed in the
/usr/local/nagios/etc directory. 

Edit the
/usr/local/nagios/etc/objects/contacts.cfg 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/objects/contacts.cfg
Configure the web interface

# make install-webconf
Create the nagiosadmin account for logging into the web interface

# htpasswd -c /usr/local/nagios/etc/htpasswd.users nagiosadmin
Restart Httpd

# service httpd restart
Download the plugins 
# tar xzf nagios-plugin (tab)

# cd nagios-plugins (tab)

Compile and install the plugins

# ./configure --with-nagios-user=nagios –with-nagios-group=nagios

# make

# make install
Add nagios to the system services and have it start when system

# chkconfig --add nagios

# chkconfig nagios on
Verify the nagios configuration files

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

# service nagios start
Find out if you have SELinux in Enforced mode


Run the following commands 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/
Log into the nagios web interface

Username will be nagiosadmin unless you specified different, plus the password you have set. 
You can also add numerous extras from Nagios Exchange.

If you try to access the web interface remotely and the page
doesn’t load, check to see if you have IPTABLES enabled

service iptables status

If you don’t see entries for port 80 and/or 443, then it is being

Allow http and https services through

vi /etc/sysconfig/iptables

Add the following entries:

-A INPUT -m state --state NEW -m tcp -p tcp --dport 80 -j ACCEPT
-A INPUT -m state --state NEW -m tcp -p tcp --dport 443 -j ACCEPT

Author: Paul Anthony McGowan

Web Technology & Linux Enthusiast, Javascript Afficiado, General Observer Of World Corruption. Builder Of A Variety Of Web Properties And Campaigner Against Serious Government Criminality. Founder of Vorteasy

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