How to Install Nagios 4.3.2 on CentOS 7 / RHEL 7

NagiosNagios is the most widely used open source monitoring tools which help us to monitor the services and application that run’s on Windows, Linux, Routers and other network devices. With the help of Nagios, you can monitor basic services and attributes. We can access the Nagios using web interface coming with the bundle and configuration need to be done on the file level.

What’s New:

  • Core Workers are the lightweight process whose job is to perform checks, due to this they do perform checks much more quickly than the old process.
  • Nagios Core process using in-memory techniques, eliminating the disk I/O latencies that could previously slow things down in a large installation.
  • Each configuration item is verified only once.
  • The host address attribute is now optional.
  • Bothe hosts and services now support an hourly value attribute.

More feature can be found here.

Services List:

This Tutorial describes how you can monitor “private” services and attributes of Linux/UNIX servers, such as:

Attributes:

  • CPU load
  • Memory usage
  • Disk usage
  • Logged in users
  • Running processes
  • etc.

Private Services:

  • HTTP
  • FTP
  • SSH
  • SMTP
  • etc

Prerequisites:

Before installing the Nagios, the system needs to meet the requirements for installing Nagios. So install the Web Server (httpd), PHP, compilers and development libraries.

READ: Install LAMP Server on CentOS 7 / RHEL 7

Install all packages in a single command.

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

Create a nagios user and nagcmd group for allowing the external commands to be executed through the web interface, add the nagios and apache user to be a part of nagcmd group.

useradd nagios
groupadd nagcmd
usermod -a -G nagcmd nagios
usermod -a -G nagcmd apache

Download latest Nagios Core.

cd /tmp/
wget https://assets.nagios.com/downloads/nagioscore/releases/nagios-4.3.2.tar.gz
tar -zxvf /tmp/nagios-4.*.tar.gz
cd /tmp/nagios-4.*

Compile and Install Nagios.

./configure --with-nagios-group=nagios --with-command-group=nagcmd
make all
make install
make install-init
make install-config
make install-commandmode

Install & Configure Nagios Web Interface:

Install the Nagios web configuration using the following command.

make install-webconf

Run the following command to install a Nagios exfoliation theme

make install-exfoliation

Create a user account (nagiosadmin) for logging into the Nagios web interface. Remember the password that you assign to this user – you’ll need it later.

htpasswd -c /usr/local/nagios/etc/htpasswd.users nagiosadmin

Restart Apache web server to make the new settings take effect.

systemctl restart httpd.service
systemctl enable httpd.service

Configure Nagios:

Sample configuration files have now been installed in the /usr/local/nagios/etc directory. These sample files should work fine for getting started with Nagios. You’ll need to make just one change before you proceed…

Edit the /usr/local/nagios/etc/objects/contacts.cfg config file with your favorite editor 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

Change the Email address field to receive the notification.

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                           admin@itzgeek.com       ; <<***** CHANGE THIS TO YOUR EMAIL ADDRESS ******
        }

Download and Install Nagios Plugins:

Download Nagios Plugins to /tmp directory.

cd /tmp
wget https://nagios-plugins.org/download/nagios-plugins-2.2.1.tar.gz
tar -zxvf /tmp/nagios-plugins-*.tar.gz
cd /tmp/nagios-plugins-*/

Compile and install the Nagios plugins.

./configure --with-nagios-user=nagios --with-nagios-group=nagios
make
make install

Start Nagios Server:

Verify the sample Nagios configuration files.

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

If there are no errors, then start the Nagios service.

service nagios start

Start Nagios on system startup.

chkconfig nagios on

SELinux:

See if SELinux is in Enforcing mode.

getenforce

Put SELinux in Permissive mode or Disable it.

setenforce 0

To make this change permanent, you’ll have to modify the settings in /etc/selinux/config and reboot.

Iptables:

Make sure to allow web server access through the firewall.

firewall-cmd --permanent --zone=public --add-service=http
firewall-cmd --reload

Access Web Interface:

Now access the Nagios web interface using the following URL. You’ll be prompted for the username (nagiosadmin) and password you specified earlier.

http://your-ip-add-ress/nagios/
Install Nagios 4.3.2 on CentOS 7 - Login Screen
Install Nagios 4.3.2 on CentOS 7 – Login Screen

Nagios console will look like below.

Install Nagios 4.3.2 on CentOS 7 - Home Page
Install Nagios 4.3.2 on CentOS 7 – Home Page

Click on Hosts in the left pane to get a list of systems being monitored by Nagios. We have not added any host to Nagios, So it simply monitors the localhost itself. To monitor a remote Linux system,

READ: Monitor Remote Linux System with Nagios Server

Install Nagios 4.3.2 on CentOS 7 - Hosts List
Install Nagios 4.3.2 on CentOS 7 – Hosts List

Click on Service in the left pane to get the status of any services that is being monitored with Nagios.

Install Nagios 4.3.2 on CentOS 7 - Services
Install Nagios 4.3.2 on CentOS 7 – Services

That’s All. In our next article, we will monitor Remote Linux System with Nagios Server.

How to Install Nagios 4.3.2 on CentOS 7 / RHEL 7
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  • Ahmed

    Hi Raj,

    i just have installed nagios, and it worked fine, but after restarting the centos VM. i was not able to login to nagios. i followed all your steps and after that i was able to login. but when i did the restart again and wasnt able to login to nagios.
    would you be able to guide me through what could be the issue.

    • Raj

      Dear Ahmed,

      I have updated the article, the following has been added extra in article.
      Auto start the services, Iptables entry, Make sure to disable selinux

      PS: Let me know

      • Ahmed

        Thanks Raj,
        yes that was the issue, and now it works fine.Thanks

  • space-hunter

    for check_http with SSL enabled,
    you have to install openssl-devel befor compile the nagios-plugins
    yum -y install openssl-devel

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