Network Monitoring Application

Nagios

 It is an Open Source system and network monitoring application. It watches hosts and services and alerting you when things go bad and when they get better.

Nagios Features:-

●     Monitoring of network services (SMTP, POP3, HTTP, NNTP, PING, etc.)

●     Monitoring of host resources (processor load, disk usage, etc.)

●     Simple plugin design that allows users to easily develop their own service checks

●     Parallelized service checks

●     Ability to define network host hierarchy using "parent" hosts, allowing detection of and distinction between hosts that are down and those that are unreachable

●     Contact notifications when service or host problems occur and get resolved (via email, pager, or user-defined method)

●     Ability to define event handlers to be run during service or host events for proactive problem resolution

●     Automatic log file rotation

●     Support for implementing redundant monitoring hosts

●     Optional web interface for viewing current network status, notification and problem history, log file, etc.

How Nagios WORKs:-

●     Nagios will execute the check_nrpe plugin and tell what service is monitor ,it contacts the NRPE deamon on the remote host through the ssl connection.

●     Then the nrpe daemon runs the nagios plugin to monitor the service and the result pass to the nagios back to the monitoring host.

DIRECT CHECK:--

●     Monitor the local service of the remote host like disk usage ,memory usage ,current users ,processes, etc.

INDIRECT CHECKS:--

●     Monitor the public services of the other systems which is not reachable directly to the monitoring server through the remote host which is directly connect to the monitoring server.

===========================

NRPE:

The NRPE addon consists of two pieces:

– The check_nrpe plugin, which resides on the local monitoring machine

– The NRPE daemon, which runs on the remote Linux/Unix machine.

Process FLOW:-

Nagios Server (check_nrpe) —–> Remote host (NRPE deamon) —–> check_disk

Nagios Server (check_nrpe) <—– Remote host (NRPE deamon) <—– check_disk (returns disk space usage)

Nagios server and nagios plugin installations steps.

Step 1: Install Required Dependencies

We need to install Apache, PHP and some libraries like gcc, glibc, glibc-common and GDlibraries and its development libraries before installing Nagios 4.0.1 with source. And to do so we can use yum default package installer.

[root@soni-laptop]# yum install -y httpd php gcc glibc glibc-common gd gd-devel make net-snmp 

Step 2: Create Nagios User and Group

Create a new nagios user and nagcmd group account and set a password.

[root@soni-laptop]# useradd nagios

[root@soni-laptop]# groupadd nagcmd

Next, add both the nagios user and the apache user to the nagcmd group.

[root@soni-laptop]# usermod -G nagcmd nagios

[root@soni-laptop]# usermod -G nagcmd apache

Step 3: Download Nagios Core 4.0.1 and Nagios Plugin 1.5

Create a directory for your Nagios installation and all its future downloads.

[root@soni-Kmint]# mkdir /root/nagios

[root@soni-Kmint]# cd /root/nagios

Now download latest Nagios Core 4.0.1 and Nagios plugins 1.5 packages with wget command.

[root@soni-Kmint nagios~]# wget http://prdownloads.sourceforge.net/sourceforge/nagios/nagios-4.0.1.tar.gz

[root@soni-Kmint nagios~]# wget https://www.nagios-plugins.org/download/nagios-plugins-1.5.tar.gz

Step 4: Extract Nagios Core and its Plugins

We need to extract downloaded package with tar command as follows.

[root@soni-Kmint nagios~]# tar –xvf nagios-4.0.1.tar.gz

[root@soni-Kmint nagios~]# tar –xvf nagios-plugins-1.5.tar.gz

When you extract these tarballs with tar command, two new folders will appear in that directory.

[root@soni-Kmint nagios ~]# ll

total 3712

drwxrwxr-x 18 root root    4096 Oct 17 03:28 nagios-4.0.1

-rw-r--r--  1 root root 1695367 Oct 15 19:49 nagios-4.0.1.tar.gz

drwxr-xr-x 15  200  300    4096 Oct 14 10:18 nagios-plugins-1.5

-rw-r--r--  1 root root 2428258 Oct  2 11:27 nagios-plugins-1.5.tar.gz

Configure Nagios Core

Now, first we will configure Nagios Core and to do so we need to go to Nagios directory and run configure file and if everything goes fine, it will show the output in the end as sample output. Please see below.

[root@soni-Kmint nagios~]# cd nagios-4.0.1

[root@soni-Kmint nagios-4.0.1 ]# ./configure --with-command-group=nagcmd

Sample output:

Nagios executable:  nagios

        Nagios user/group:  nagios,nagios

       Command user/group:  nagios,nagcmd

             Event Broker:  yes

        Install ${prefix}:  /usr/local/nagios

    Install ${includedir}:  /usr/local/nagios/include/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/

 Traceroute (used by WAP):  /bin/traceroute

 Review the options above for accuracy.  If they look okay,

type 'make all' to compile the main program and CGIs.

Now, after configuring we need to Compile and install all the binaries with make command and make install command will install all the needed libraries in your machine and we can proceed further.

[root@soni-Kmint nagios-4.0.1 ]# make all

[root@soni-Kmint nagios-4.0.1 ]# make install

Sample output:

*** Main program, CGIs and HTML files installed ***

 You can continue with installing Nagios as follows (type 'make'

without any arguments for a list of all possible options):

 make install-init

 - This installs the init script in /etc/rc.d/init.d

  make install-commandmode

This installs and configures permissions on the

directory for holding the external command file

 =>  make install-config #This installs sample config files in /usr/local/nagios/etc

Following command will install the init scripts for Nagios..

[root@soni-Kmint nagios-4.0.1 ]# make install-init

To make nagios work from command line we need to install command-mode.

[root@soni-Kmint nagios-4.0.1 ]# make install-commandmode

Next, install sample nagios files, please run following command.

[root@soni-Kmint nagios-4.0.1 ]# make install-config

Sample output:

/usr/bin/install -c -m 775 -o nagios -g nagios -d /usr/local/nagios/etc

/usr/bin/install -c -m 775 -o nagios -g nagios -d /usr/local/nagios/etc/objects

/usr/bin/install -c -b -m 664 -o nagios -g nagios sample-config/nagios.cfg /usr/local/nagios/etc/nagios.cfg

/usr/bin/install -c -b -m 664 -o nagios -g nagios sample-config/cgi.cfg /usr/local/nagios/etc/cgi.cfg

/usr/bin/install -c -b -m 660 -o nagios -g nagios sample-config/resource.cfg /usr/local/nagios/etc/resource.cfg

/usr/bin/install -c -b -m 664 -o nagios -g nagios sample-config/template-object/templates.cfg /usr/local/nagios/etc/objects/templates.cfg

/usr/bin/install -c -b -m 664 -o nagios -g nagios sample-config/template-object/commands.cfg /usr/local/nagios/etc/objects/commands.cfg

/usr/bin/install -c -b -m 664 -o nagios -g nagios sample-config/template-object/contacts.cfg /usr/local/nagios/etc/objects/contacts.cfg

/usr/bin/install -c -b -m 664 -o nagios -g nagios sample-config/template-object/timeperiods.cfg /usr/local/nagios/etc/objects/timeperiods.cfg

/usr/bin/install -c -b -m 664 -o nagios -g nagios sample-config/template-object/localhost.cfg /usr/local/nagios/etc/objects/localhost.cfg

/usr/bin/install -c -b -m 664 -o nagios -g nagios sample-config/template-object/windows.cfg /usr/local/nagios/etc/objects/windows.cfg

/usr/bin/install -c -b -m 664 -o nagios -g nagios sample-config/template-object/printer.cfg /usr/local/nagios/etc/objects/printer.cfg

/usr/bin/install -c -b -m 664 -o nagios -g nagios sample-config/template-object/switch.cfg /usr/local/nagios/etc/objects/switch.cfg

*** Config files installed ***

Remember, these are *SAMPLE* config files.  You'll need to read

the documentation for more information on how to actually define

services, hosts, etc. to fit your particular needs.

Step 5: Customizing Nagios Configuration

Open the “contacts.cfg” file with your choice of editor and set the email addressassociated with the nagiosadmin contact definition to receiving email alerts.

# vi /usr/local/nagios/etc/objects/contacts.cfg

Sample Output

# CONTACTS

# Just one contact defined by default - the Nagios admin (that's you)

# This contact definition inherits a lot of default values from the 'generic-contact'

# template which is defined elsewhere.

 define contact{

       contact_name                    nagiosadmin             ; Short name of user

       use                             generic-contact         ; Inherit default values from generic-contact template (defined above)

       alias                           Nagios Admin            ; Full name of user

  email                           soni-Kmint@soni-Kmint.com     ; *** CHANGE THIS TO YOUR EMAIL ADDRESS ****

       }

Step 6: Install and Configure Web Interface for Nagios

We are done with all configuration in the backend, now we will configure Web Interface For Nagios with following command. The below command will Configure Web interface for Nagios and a web admin user will be created “nagiosadmin”.

[root@soni-Kmint nagios-4.0.1 ]# make install-webconf

In this step, we will be creating a password for “nagiosadmin”. After executing this command, please provide a password twice and keep it remember because this password will be used when you login in the Nagios Web interface.

[root@soni-Kmint nagios-4.0.1]# htpasswd -s -c /usr/local/nagios/etc/htpasswd.users nagiosadmin

New password:

Re-type new password:

Adding password for user nagiosadmin

Restart Apache to make the new settings take effect.

[root@soni-Kmint ]# service httpd start (On RedHat / CentOS)

[root@soni-Kmint ]# systemctl start httpd.service (On Fedora)

Step 7: Compile and Install Nagios Plugin

We have downloaded nagios plugins in /root/nagios, Go there and configure and install it as directed below.

[root@soni-Kmint nagios]# cd /root/nagios

[root@soni-Kmint nagios]# cd nagios-plugins-1.5

[root@soni-Kmint nagios]# ./configure --with-nagios-user=nagios --with-nagios-group=nagios

[root@soni-Kmint nagios]# make

[root@soni-Kmint nagios]# make install

Step 8: Verify Nagios Configuration Files

Now we are all done with Nagios configuration and its time to verify it and to do so please insert following command. If everything goes smooth it will show up similar to below output.

[root@soni-Kmint nagios]# /usr/local/nagios/bin/nagios -v /usr/local/nagios/etc/nagios.cfg

Sample Output

/usr/bin/install -c -m 644 sample-config/httpd.conf /etc/httpd/conf.d/nagios.conf

 *** Nagios/Apache conf file installed ***

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

Step 9: Add Nagios Services to System Startup

To make Nagios work across reboots, we need to add nagios and httpd with chkconfigcommand.

[root@soni-Kmint ]# chkconfig --add nagios

[root@soni-Kmint ]# chkconfig --level 35 nagios on

[root@soni-Kmint ]# chkconfig --add httpd

[root@soni-Kmint ]# chkconfig --level 35 httpd on

Restart Nagios to make the new settings take effect.

[root@soni-Kmint ]# service nagios start (On RedHat / CentOS)

[root@soni-Kmint ]# systemctl start nagios.service (On Fedora)