How to install Nagios on CentOS 7

Learn how to install Nagios on CentOS 7 with this step-by-step guide. Set up this powerful monitoring tool to keep your systems and networks running smoothly. #centlinux #linux #nagios

What is Nagios?

Nagios Core is a free and open source software application that provides monitoring and alerting services for servers, switches, applications and services. It monitors targets (i.e. hosts and services) and alerts users when something go wrong and alerts them a second time when the problem has been resolved. Nagios Core is primary application and monitoring and alerting engine, around that hundred of Nagios Projects are built.

In this article, we will install Nagios on CentOS 7. But before moving forward, it is required to have basic concepts of Nagios Core 4. Therefore, it is highly recommended that you should have Learning Nagios – Third Edition (PAID LINK). It will be really helpful for you during your Nagios journey.

System Specification

We have configured a CentOS 7 virtual machine with following specifications:

• Operating System – CentOS 7.6
• Nagios Core – 4.4.2
• Hostname – nagios-01.example.com
• IP Address: – 192.168.116.130/24

Install Nagios on CentOS 7

Connect to nagios-01.example.com using ssh.

Install prerequisite packages using yum command.

# yum install -y gcc glibc glibc-common wget unzip httpd php gd gd-devel perl postfix

Currently, Nagios Core does not compliance with SELinux, therefore we have to disable SELinux.

# sed -i 's/SELINUX=.*/SELINUX=disabled/g' /etc/selinux/config
# setenforce 0

Create a directory for downloading Nagios Core source.

# mkdir setup

Download Nagios Core from https://www.nagios.org/downloads/nagios-core/.

# cd ~/setup
# wget https://assets.nagios.com/downloads/nagioscore/releases/nagios-4.4.2.tar.gz
--2018-12-23 10:35:22--  https://assets.nagios.com/downloads/nagioscore/releases/nagios-4.4.2.tar.gz
Resolving assets.nagios.com (assets.nagios.com)... 72.14.181.71, 2600:3c00::f03c:91ff:fedf:b821
Connecting to assets.nagios.com (assets.nagios.com)|72.14.181.71|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 11301454 (11M) [application/x-gzip]
Saving to: ânagios-4.4.2.tar.gzâ

100%[======================================>] 11,301,454  1.16MB/s   in 10s

2018-12-23 10:35:34 (1.03 MB/s) - ânagios-4.4.2.tar.gzâ saved [11301454/11301454]

Extract downloaded source of Nagios Core.

# tar xf nagios-4.4.2.tar.gz

Compile and install Nagios Core from extracted source.

# cd ~/setup/nagios-4.4.2
# ./configure
config.status: creating t/Makefile
config.status: creating t-tap/Makefile
config.status: creating include/config.h
config.status: creating lib/snprintf.h
config.status: creating lib/iobroker.h

Creating sample config files in sample-config/ ...


*** Configuration summary for nagios 4.4.2 2018-08-16 ***:

 General Options:
 -------------------------
        Nagios executable:  nagios
        Nagios user/group:  nagios,nagios
       Command user/group:  nagios,nagios
             Event Broker:  yes
        Install ${prefix}:  /usr/local/nagios
    Install ${includedir}:  /usr/local/nagios/include/nagios
                Lock file:  /run/nagios.lock
   Check result directory:  /usr/local/nagios/var/spool/checkresults
           Init directory:  /lib/systemd/system
  Apache conf.d directory:  /etc/httpd/conf.d
             Mail program:  /usr/sbin/sendmail
                  Host OS:  linux-gnu
          IOBroker Method:  epoll

 Web Interface Options:
 ------------------------
                 HTML URL:  http://localhost/nagios/
                  CGI URL:  http://localhost/nagios/cgi-bin/
 Traceroute (used by WAP):


Review the options above for accuracy.  If they look okay,
type 'make all' to compile the main program and CGIs.

# make all
...
make[1]: Entering directory `/root/setup/nagios-4.4.2/worker'
cd ./ping && make all
make[2]: Entering directory `/root/setup/nagios-4.4.2/worker/ping'
gcc -I.. -I ../../include -I ../.. -g -O2 -DHAVE_CONFIG_H -o worker-ping worker-ping.c -L ../../lib -l nagios
make[2]: Leaving directory `/root/setup/nagios-4.4.2/worker/ping'
make[1]: Leaving directory `/root/setup/nagios-4.4.2/worker'

*** Compile finished ***

If the main program and CGIs compiled without any errors, you
can continue with testing or installing Nagios as follows (type
'make' without any arguments for a list of all possible options):

  make test
     - This runs the test suite

  make install
     - This installs the main program, CGIs, and HTML files

  make install-init
     - This installs the init script in /lib/systemd/system

  make install-daemoninit
     - This will initialize the init script
       in /lib/systemd/system

  make install-groups-users
     - This adds the users and groups if they do not exist

  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
       You'll have to modify these sample files before you can
       use Nagios.  Read the HTML documentation for more info
       on doing this.  Pay particular attention to the docs on
       object configuration files, as they determine what/how
       things get monitored!

  make install-webconf
     - This installs the Apache config file for the Nagios
       web interface

  make install-exfoliation
     - This installs the Exfoliation theme for the Nagios
       web interface

  make install-classicui
     - This installs the classic theme for the Nagios
       web interface


*** Support Notes *******************************************

If you have questions about configuring or running Nagios,
please make sure that you:

     - Look at the sample config files
     - Read the documentation on the Nagios Library at:
           
Nagios Library


before you post a question to one of the mailing lists.
Also make sure to include pertinent information that could
help others help you.  This might include:

     - What version of Nagios you are using
     - What version of the plugins you are using
     - Relevant snippets from your config files
     - Relevant error messages from the Nagios log file

For more information on obtaining support for Nagios, visit:

       
Nagios Support Home


*************************************************************

Enjoy.

Create OS user and groups for Nagios Core.

# make install-groups-users
groupadd -r nagios
useradd -g nagios nagios
# usermod -a -G nagios apache

Install Nagios on CentOS 7 now.

# make install
/usr/bin/install -c -m 775 -o nagios -g nagios -d /usr/local/nagios/libexec
/usr/bin/install -c -m 775 -o nagios -g nagios -d /usr/local/nagios/var
/usr/bin/install -c -m 775 -o nagios -g nagios -d /usr/local/nagios/var/archives
/usr/bin/install -c -m 775 -o nagios -g nagios -d /usr/local/nagios/var/spool/checkresults
chmod g+s /usr/local/nagios/var/spool/checkresults

*** 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 /lib/systemd/system

  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

make[1]: Leaving directory `/root/setup/nagios-4.4.2'

Install Nagios Core service.

# make install-daemoninit
/usr/bin/install -c -m 755 -d -o root -g root /lib/systemd/system
/usr/bin/install -c -m 755 -o root -g root startup/default-service /lib/systemd/system/nagios.service
Created symlink from /etc/systemd/system/multi-user.target.wants/nagios.service to /usr/lib/systemd/system/nagios.service.

*** Init script installed ***

Enable httpd service.

# systemctl enable httpd.service
Created symlink from /etc/systemd/system/multi-user.target.wants/httpd.service to /usr/lib/systemd/system/httpd.service.

Install and configure external command file.

# make install-commandmode
/usr/bin/install -c -m 775 -o nagios -g nagios -d /usr/local/nagios/var/rw
chmod g+s /usr/local/nagios/var/rw

*** External command directory configured ***

Install Sample configuration files for Nagios Core.

# make install-config
/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.

Add Nagios Core configurations to Apache Web Server.

# make install-webconf
/usr/bin/install -c -m 644 sample-config/httpd.conf /etc/httpd/conf.d/nagios.conf
if [ 0 -eq 1 ]; then 
        ln -s /etc/httpd/conf.d/nagios.conf /etc/apache2/sites-enabled/nagios.conf; 
fi

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

Configure Linux Firewall

Configure Linux Firewall to allow http service.

# firewall-cmd --permanent --add-service=http
success
# firewall-cmd --reload
success

Setup Basic HTTP Authentication

Nagios does not have integrated user authentication, therefore, we have to use Basic HTTP authentication for this purpose.

Create an admin user for Nagios Core Web UI.

# htpasswd -c /usr/local/nagios/etc/htpasswd.users nagiosadmin
New password:
Re-type new password:
Adding password for user nagiosadmin

Start httpd & nagios services.

# systemctl start httpd.service
# systemctl start nagios.service
Warning: nagios.service changed on disk. Run 'systemctl daemon-reload' to reload units.
# systemctl daemon-reload

Access Nagios Web Interface

Browse URL http://192.168.116.130/nagios to connect with Nagios Core Web UI.

Login using nagiosadmin user.

Go to services page.

You can see that all the services are unavailable. It is because we don’t have installed Nagios Plugins on our CentOS 7 server.

Install Nagios Plugins on CentOS 7

Install prerequisite packages for Nagios Plugins using yum command.

# yum install -y perl-Net-SNMP gcc glibc glibc-common make gettext automake autoconf wget openssl-devel net-snmp net-snmp-utils epel-release

Download Nagios Plugins from https://www.nagios.org/downloads/nagios-plugins/.

# cd ~/setup
# wget https://nagios-plugins.org/download/nagios-plugins-2.2.1.tar.gz
--2018-12-23 10:37:19--  https://nagios-plugins.org/download/nagios-plugins-2.2.1.tar.gz
Resolving nagios-plugins.org (nagios-plugins.org)... 72.14.186.43
Connecting to nagios-plugins.org (nagios-plugins.org)|72.14.186.43|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 2728818 (2.6M) [application/x-gzip]
Saving to: ânagios-plugins-2.2.1.tar.gzâ

100%[======================================>] 2,728,818    813KB/s   in 3.3s

2018-12-23 10:37:24 (813 KB/s) - ânagios-plugins-2.2.1.tar.gzâ saved [2728818/2728818]

Extract downloaded source of Nagios Plugins.

# cd ~/setup
# tar xf nagios-plugins-2.2.1.tar.gz

Compile Nagios Plugins source.

# cd ~/setup/nagios-plugins-2.2.1
# ./configure
...
config.status: executing libtool commands
config.status: executing po-directories commands
config.status: creating po/POTFILES
config.status: creating po/Makefile

Install Nagios Plugins by executing following command.

# make
...
make[2]: Nothing to be done for `all'.
make[2]: Leaving directory `/root/setup/nagios-plugins-2.2.1/po'
make[2]: Entering directory `/root/setup/nagios-plugins-2.2.1'
make[2]: Leaving directory `/root/setup/nagios-plugins-2.2.1'
make[1]: Leaving directory `/root/setup/nagios-plugins-2.2.1'

# make install
...
make[2]: Entering directory `/root/setup/nagios-plugins-2.2.1'
make[2]: Nothing to be done for `install-exec-am'.
make[2]: Nothing to be done for `install-data-am'.
make[2]: Leaving directory `/root/setup/nagios-plugins-2.2.1'
make[1]: Leaving directory `/root/setup/nagios-plugins-2.2.1'

Go to Nagios Web UI and open services page.

You can see that, now all the services are in OK state now. (Note: Keep patience, Nagios Core takes a while to collect data for each service)

Recommended Training for You: Network Monitoring Using Nagios

Final Thoughts

Installing Nagios on CentOS 7 ensures you have a robust monitoring solution for your systems and networks. By following this guide, you should now have Nagios up and running efficiently.

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