Install & Configure Nagios Core 4.4 on CentOS 7


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 and configure Nagios Core 4.4 on CentOS 7 server.

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.


This Article Provides:


System Specification:

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

  • Operating System - CentOS 7.6
  • Nagios Core - 4.4.2
  • Hostname -
  • IP Address: -


Install Nagios Core 4.4 on CentOS 7:

Connect to using ssh.

Install pre-requisite 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

# cd ~/setup
# wget
--2018-12-23 10:35:22--
Resolving (, 2600:3c00::f03c:91ff:fedf:b821
Connecting to (||: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:

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:



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 Core 4.4 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/ to /usr/lib/systemd/system/nagios.service.

*** Init script installed ***

Enable httpd service.

# systemctl enable httpd.service
Created symlink from /etc/systemd/system/ 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; \

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

Configure Linux Firewall to allow http service.

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

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

Browse URL 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 Server:

Install pre-requisite 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

# cd ~/setup
# wget
--2018-12-23 10:37:19--
Resolving (
Connecting to (||: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.

# 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)

We have successfully install and configure Nagios Core 4.4 on our CentOS 7 server.


  1. I Like your work highly appreciate

  2. Hi Ahmer,

    Thank you for the configuration. I wanted to monitor backup job status from veritas backup exec but I am getting unknown error which is "unknown command check_backupexec".

    Details of Nagios: Nagios 4.4.2 in CentOS 7. Veritas backup verion 20, 2018.

    1. Hi,
      Thanks for liking this article.

      Make sure you have defined the command check_backupexec in command.cfg file.
      It looks like you are using BackupExec plugin. Please refer to BackupExec - Nagios Exchange for complete configuration.

  3. Hi Ahmer,
    I am faceing the following issue while following your blog:
    systemctl start nagios.service
    Failed to start nagios.service: Unit not found.

    Can you please guide. How to start nagios service.

    1. It looks like nagios service is not correctly installed.
      Please ensure that you have installed nagios daemon using (as mentioned in above article).
      # make install-daemoninit

  4. how to configure snmp for nagios to monitor hard disk, cpu and etc.

    1. There are some templates available in Nagios default configurations for capturing SNMP traps from network devices. Just configure SNMP traps on that device and configure a service on you Nagios Core server to capture that SNMP trap.

  5. Hi Ahmer,

    Brilliant peace thank you for that!

    Somehow follwing your instructions i must have missed a step, because i am able to start en reload the nagios service and i am also able te see the test appache webpage, but
    When i put in the ipaddress/nagios into the url of my webbrowser it can't find anything :(
    The webpage cannot be found

    Could you please guide my into the right direction of the step i might have missed?

    thanks you!

    1. Hi, Thanks for appreciating my work.

      - For Nagios Service, use following command to verify and troubleshoot errors in Nagios configurations.

      - For Apache Service, refer to /var/log/messages for any possible errors.

  6. how to install ndoutil on nagios ?

  7. Can I add China skyline gateway for monitoring in nagios ???
    If yes how can I add ?

    1. Yes, you can.
      You have to enable SNMP Traps, and allow Nagios Server to access the router SNMP traps.

    2. Thanks or the reply.
      Can you guide me through ???

  8. thanks you ,
    i have a question please , i wan't to add supervisor can you show me what i should i do ?

    1. Nagios Core uses HTTP basic authentication and Nagios Core's default password file is /usr/local/nagios/etc/htpasswd.users.

      You can use htpasswd command to add a supervisor user therein.

    2. Thanks you MR Ahmed,
      What about NRPE,apache, postgress ?
      I want to connect Nagios with server in my vmwork .

    3. Hi, NRPE installation is already mentioned here.

      You need to create services in Nagios to monitor services like Apache, Postgres, etc.

      If you are working on a DIY strategy than, I suggest you to please read Learning Nagios - Third Edition.

  9. Hi Ahmer,

    can u help me to configure the SMTP for email notifications

  10. pls provide the proper steps to install NSclient in windows

  11. Hi Ahmer,
    Can you share the post for Naemon thruk installation and configurationd

    1. Hi, I didn't work on it. But consider your request and will write on it soon.

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