Nagios Commands and interview questions answers
Nagios is an open-source software for continuous monitoring of systems, networks and
infrastructure. It runs plugins stored on a server which is connected with a host or another servr
on your network or the internet. In case of any failure Nagios alerts about the issues so that the
technical team can perform recovery process immediately.
History of Nagios:
➢ In the year 1999, Ethan Galstad developed it as a part of netsaint distribution.
➢ 2002, ethan renames the project to “Nagios” because of trademark issues with the name
“netsaint”.
➢ 2009, Nagios releases its first commercial version, Nagios XI.
➢ In 2012, Nagios again renamed as Nagios core.
➢ It uses port number 5666, 5667 and 5668 to monitor its client.
Why Nagios?
➢ Detect all types of network or server issues.
➢ Helps to find the root cause of the problem which allow you to get the permanent
solution to the problem.
➢ Reduce downtime.
➢ Active monitoring of entire infrastructure.
➢ Allow you to monitor and troubleshoot server performance issues.
➢ Automatically fix problems.
Features of Nagios:
➢ Oldest and latest.
➢ Good log and database system.
➢ Informative and attractive web interface.
➢ Automatically send alerts if condition changes.
➢ Helps you to detect network errors or server crashes.
➢ You can monitor the entire business process and IT infrastructure with a single pass.
➢ Monitor network services like http, smtp, snmp, ftp, ssh, pop, DNS, LDAP, IPMI etc.
Phases of Continuous Monitoring:
1. Define: develop a monitoring strategy
2. Establish: how frequently you are going to monitor it.
3. Implement
4. Analyze data and report finding
5. Respond
6. Review and update
Nagios Architecture:
Nagios is a client-server architecture. Usually on a network, a Nagios server is running on
a host and plugins are running on all the remote host which should you monitor.
How does Nagios works?
➢ Mention all details in configuration files.
➢ Daemon read those details what data to be collected.
➢ Daemon use NRPE plugins to collect data from nodes and store in its own database.
➢ Finally shows everything in dashboard.
Pre-requisites:
• Httpd (browser)
• Php (dashboard)
• Gcc and gd (compiler)
• Makefile (to build)
• Perl (script)
Main configuration file: /usr/local/Nagios/etc.Nagios.cfg
All monitoring things called as service.
For e.g: 5 servers — 4 checks each
Then you have to monitor 5*4= 20 services
Dashboard overview:
In dashboard you can see
Host: down, unreachable, up, recovery, none
Service: warning, unknown, critical, recovery, pending
Installation of Nagios on Linux:
To start Nagios core installation, you must have your EC2 instance up and run and have already
configured SSH access to the instance.
Step-1: install pre-requisites software on your EC2 machine prior to Nagios installation like
apache, php, gcc compiler and gd development libraries.
# sudo su
# yum install httpd php
# yum install gcc glibc glibc-common
# yum install gd gd-devel
Step-2: create account information you need to setup a Nagios user, run the following
commands,
# adduser -m Nagios
# passwd Nagios
Now it will ask to enter new password give ‘12345’ as password.
# groupadd Nagioscmd
# usermod -a -G Nagioscmd Nagios
# usermod -a -G Nagioscmd apache
Step-3: download Nagios core and the plugins. Create a directory for storing the downloads.
# mkdir ~/downloads
# cd ~/downloads
Download the source code tarballs of both Nagios and the Nagios plugins.
# wget http://prdownloads.sourceforge.net/sourceforge/Nagios/Nagios-4.0.8.tar.gz
#wget http://Nagios-plugins.org/download/Nagios-plugins-2.0.3.tar.gz
Step-4: complete and install Nagios extract the Nagios source code tarball
# tar zxvf Nagios-4.0.8.tar.gz
# cd Nagios-4.0.8
Run the configuration script with the name of the group which you have create in above step.
# ./configure –with-command-grouo=Nagioscmd
Compile the Nagios source code
# make all
Install binaries, init script, sample config files and set permissions on the external command
directly.
# make install
# make install-init
# make install-config
# make install-commandmode
Setp-5: configure the web interface
# make install-webconf
Step-6: create a ‘Nagiosadmin’ account for login into Nagios web interface, set password as
well.
# htpasswd -c /usr/local/Nagios/etc/htpasswd.users Nagiosadmin
Asking for a password, set a new pwd
# service httpd restart
Step-7: compile and install the Nagios plugins. Extract the Nagios plugins source code tarball.
# cd ~/downloads
# tar zxvf Nagios-plugins-2.0.3.tar.gz
# cd Nagios-plugins-2.0.3
Compile and install the plugins
# ../configure — with-Nagios-user=Nagios — with-Nagios-group=Nagios
# make
# make install
Step-8: start Nagios. Add Nagios to the list of system services and have it automatically start
when the system boots.
# chkconfig — add Nagios
# chkconfig Nagios on
Verify the sample Nagios configuration files
# /usr/local/Nagios/bin/Nagios -v
# usr/local/Nagios/etc/Nagios.cfg
If there are no errors, start Nagios
# service Nagios start
# service httpd restart
Step-9: copy public ip of EC2 instance and paste in google chrome, in given way
For e.g 20.1.1.1/Nagios/Nagios
Ask for username- Nagiosadmin
Password-
