Procedure

1. Install the prerequisites:

   [user@nagios]# yum install -y httpd php php-cli gcc glibc glibc-common gd gd-devel net-snmp openssl openssl-devel wget unzip

2. Open port 80 for httpd:

   [user@nagios]# firewall-cmd --zone=public --add-port=80/tcp
   [user@nagios]# firewall-cmd --zone=public --add-port=80/tcp --permanent

3. Create a user and group for Nagios Core:

   [user@nagios]# useradd nagios
   [user@nagios]# passwd nagios
   [user@nagios]# groupadd nagcmd
   [user@nagios]# usermod -a -G nagcmd nagios
   [user@nagios]# usermod -a -G nagcmd apache

4. Download the latest version of Nagios Core and Plug-ins:

   [user@nagios]# wget --inet4-only https://assets.nagios.com/downloads/nagioscore/releases/nagios-4.3.1.tar.gz
   [user@nagios]# wget --inet4-only http://www.nagios-plugins.org/download/nagios-plugins-2.2.1.tar.gz
   [user@nagios]# tar zxf nagios-4.3.1.tar.gz
   [user@nagios]# tar zxf nagios-plugins-2.2.1.tar.gz
   [user@nagios]# cd nagios-4.3.1

5. Run ./configure:

   [user@nagios]# ./configure --with-command-group=nagcmd

6. Compile the Nagios Core source code:

   [user@nagios]# make all

7. Install Nagios source code:

   [user@nagios]# make install
   [user@nagios]# make install-init
   [user@nagios]# make install-config
   [user@nagios]# make install-commandmode
   [user@nagios]# make install-webconf

8. Copy the event handlers and change their ownership:

   [user@nagios]# cp -R contrib/eventhandlers/ /usr/local/nagios/libexec/
   [user@nagios]# chown -R nagios:nagios /usr/local/nagios/libexec/eventhandlers

9. Run the pre-flight check:

   [user@nagios]# /usr/local/nagios/bin/nagios -v /usr/local/nagios/etc/nagios.cfg

10. Make and install the Nagios Core plug-ins:

    [user@nagios]# cd ../nagios-plugins-2.2.1
    [user@nagios]# ./configure --with-nagios-user=nagios --with-nagios-group=nagios
    [user@nagios]# make
    [user@nagios]# make install

11. Create a user for the Nagios Core user interface:

    [user@nagios]$ sudo htpasswd -c /usr/local/nagios/etc/htpasswd.users nagiosadmin

    Important

    If adding a user other than nagiosadmin, ensure the /usr/local/nagios/etc/cgi.cfg file gets updated with the username too.

    Also modify the /usr/local/nagios/etc/objects/contacts.cfg file with the user name, full name and email address as needed.

Procedure

1. Add Nagios Core as a service and enable it:

   [user@nagios]# chkconfig --add nagios
   [user@nagios]# chkconfig --level 35 nagios on

2. Start the Nagios Core daemon and Apache:

   [user@nagios]# systemctl start nagios
   [user@nagios]# systemctl enable httpd
   [user@nagios]# systemctl start httpd

Procedure

1. With Nagios up and running, log in to the web user interface:

   http://IP_ADDRESS/nagios

   Nagios Core will prompt for a user name and password.

2. Input the login and password of the default Nagios Core user.

Procedure

1. Install these packages on the node:

   [user@mon]# yum install openssl openssl-devel gcc make git

2. NRPE installation requires a Nagios user. So create the user first:

   [user@mon]# useradd nagios
   [user@mon]# passwd nagios

3. Download the latest version of the Nagios plug-ins. Then, make and install them:

   [user@mon]# wget http://www.nagios-plugins.org/download/nagios-plugins-2.2.1.tar.gz
   [user@mon]# tar zxf nagios-plugins-2.2.1.tar.gz
   [user@mon]# cd nagios-plugins-2.2.1
   [user@mon]# ./configure
   [user@mon]# make
   [user@mon]# make install

4. NRPE uses xinetd for communication. Install it before installing the NRPE module:

   [user@mon]# yum install xinetd

5. Download the latest verion of the Ceph plug-ins:

   [user@mon]# cd ~
   [user@mon]# git clone --recursive https://github.com/valerytschopp/ceph-nagios-plugins.git
   [user@mon]# cd ceph-nagios-plugins
   [user@mon]# make dist
   [user@mon]# make install

6. Download, make and install Nagios NRPE:

   [user@mon]# cd ~
   [user@mon]# wget https://github.com/NagiosEnterprises/nrpe/releases/download/nrpe-3.1.0/nrpe-3.1.0.tar.gz
   [user@mon]# tar xvfz nrpe-3.1.0.tar.gz
   [user@mon]# cd nrpe-3.1.0
   [user@mon]# ./configure
   [user@mon]# make all
   [user@mon]# make install-groups-users
   [user@mon]# make install
   [user@mon]# make install-config
   [user@mon]# make install-init

7. Edit the the /etc/services file, and add the service string nrpe 5666/tcp:

8. Open port 5666 to allow communication with NRPE:

   [user@mon]# firewall-cmd --zone=public --add-port=5666/tcp
   [user@mon]# firewall-cmd --zone=public --add-port=5666/tcp --permanent

Procedure

1. Enable, restart, and reload xinetd:

   [user@mon]# systemctl enable xinetd
   [user@mon]# systemctl restart xinetd
   [user@mon]# systemctl reload xinetd

2. Enable and start NRPE:

   [user@mon]# systemctl enable nrpe
   [user@mon]# systemctl start nrpe

Procedure

1. Edit the xinetd configuration with the Nagios server’s IP address:

   [user@mon]# vi /etc/xinetd.d/nrpe

   # default: off
   # description: NRPE (Nagios Remote Plugin Executor)
   service nrpe
   {
       disable         = yes
       socket_type     = stream
       port            = 5666
       wait            = no
       user            = nagios
       group           = nagios
       server          = /usr/local/nagios/bin/nrpe
       server_args     = -c /usr/local/nagios/etc/nrpe.cfg --inetd
       only_from       = 127.0.0.1,IP_ADDRESS_OF_NAGIOS_CORE_SERVER
       log_on_success  =
   }

2. After adding the IP address of the Nagios Core server to the only_from option, restart the xinetd service:

   [user@mon]# systemctl restart xinetd

3. Edit the NRPE configuration with the Nagios server’s IP address:

   [user@mon]# vi /usr/local/nagios/etc/nrpe.cfg

   allowed_hosts=127.0.0.1,IP_ADDRESS_OF_NAGIOS_CORE_SERVER

4. Add the IP address of the Nagios Core server to the allowed_hosts setting. Then, restart nrpe:

   [user@mon]# systemctl restart nrpe

5. Test the installation:

   [user@host]# /usr/local/nagios/libexec/check_nrpe -H localhost

   The check should echo NRPE v3.1.0-rc1 if it is working correctly.