How to Install Nagios 4.3.4 on CentOS 7/6 & RHEL 7/6

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Nagios 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.

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 the 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-4.3.4.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.

### CentOS 7 / RHEL 7 ###

systemctl restart httpd
systemctl enable httpd

### CentOS 6 / RHEL 6 ###

service httpd start
chkconfig httpd on

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.

Firewall

Make sure to allow web server access through the firewall.

### FirwallD ###

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

### IP Tables ###

iptables -I INPUT -m state --state NEW -m tcp -p tcp --dport 80 -j ACCEPT
service iptables save

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 4.3.4 on CentOS 7 - Nagios Login Screen
Install Nagios 4.3.4 on CentOS 7 – Nagios Login Screen

Nagios console will look like below.

Install Nagios 4.3.4 on CentOS 7 - Nagios Home Page
Install Nagios 4.3.4 on CentOS 7 – Nagios 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 4.3.4 on CentOS 7 - Nagios Hosts List
Install Nagios 4.3.4 on CentOS 7 – Nagios Hosts List

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

Install Nagios 4.3.4 on CentOS 7 - Monitoring Services with Nagios
Install Nagios 4.3.4 on CentOS 7 – Monitoring Services with Nagios

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

Further Reading

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How to Install Nagios 4.3.4 on CentOS 7/6 & RHEL 7/6

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