Nagios is an awesome Open Source monitoring tool, it provides you more comprehensive monitoring environment to always keep an eye on your all machines/networks whether you are in your data center or just your small labs.

With Nagios, you can monitor your remote hosts and their services remotely on a single window. It shows warnings and indicates if something goes wrong in your servers which eventually helps us to detect some problems before they occur. It helps us to reduce downtime and business losses.

Recently, Nagios released its latest versions Nagios Core 4.4.5 and its latest stable release of Nagios plugins 2.2.1 on August 20, 2019.

This article is intended to guide you with easy instructions on how to install the latest Nagios Core 4.4.5 from source (tarball) on RHEL 8/7/6, CentOS 8/7/6 and Fedora 26-30 distributions.

Within 30 minutes you will be monitoring your local machine, no advanced installation procedure only basic installation that will work 100% on most of today’s Linux servers.

Please Note: The installation instructions were shown in here are written based on CentOS 7.5 Linux distribution.

Installing Nagios 4.4.5 and Nagios Plugin 2.2.1

If you follow these instructions correctly, you will end up with the following information.

Nagios and its plugins will be installed under /usr/local/nagios directory. Nagios will be configured to monitor few services of your local machine (Disk Usage, CPU Load, Current Users, Total Processes, etc.) Nagios web interface will be available at http://localhost/nagios

Step 1: Install Required Dependencies

We need to install Apache, PHP and some libraries like gcc, glibc, glibc-common and GD libraries and its development libraries before installing Nagios 4.4.5 with the source. And to do so, we can use yum default package installer.

[[email protected]]# yum install -y httpd httpd-tools php gcc glibc glibc-common gd gd-devel make net-snmp -------------- On Fedora -------------- [[email protected]]# dnf install -y httpd httpd-tools php gcc glibc glibc-common gd gd-devel make net-snmp

Step 2: Create Nagios User and Group

Create a new nagios user using useradd command and nagcmd group account and set a password.

Next, add both the nagios user and the apache user to the nagcmd group using usermod command.

Step 3: Download Nagios Core 4.4.5 and Nagios Plugin 2.2.1

Create a directory for your Nagios installation and all its future downloads.

Now download latest Nagios Core 4.4.5 and Nagios plugins 2.2.1 packages with wget command.

Step 4: Extract Nagios Core and its Plugins

We need to extract downloaded packages with tar command as follows.

When you extract these tarballs with tar command, two new folders will appear in that directory.

[[email protected] nagios ~]# ls -l total 13520 drwxrwxr-x 18 root root 4096 Aug 20 17:43 nagios-4.4.5 -rw-r--r-- 1 root root 11101966 Aug 20 17:48 nagios-4.4.5.tar.gz drwxr-xr-x 15 root root 4096 Apr 19 12:04 nagios-plugins-2.2.1 -rw-r--r-- 1 root root 2728818 Apr 19 12:04 nagios-plugins-2.2.1.tar.gz

Configure Nagios Core

Now, first we will configure Nagios Core and to do so we need to go to Nagios directory and run configure file and if everything goes fine, it will show the output in the end as sample output. Please see below.

Sample output:

Creating sample config files in sample-config/ ... *** Configuration summary for nagios 4.4.5 2019-08-20 ***: General Options: ------------------------- Nagios executable: nagios Nagios user/group: nagios,nagios Command user/group: nagios,nagcmd 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/bin/mail 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): /usr/bin/traceroute Review the options above for accuracy. If they look okay, type 'make all' to compile the main program and CGIs.

After configuring, we need to compile and install all the binaries with make all and make install command, it will install all the needed libraries in your machine and we can proceed further.

Sample output:

*** 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

The following command will install the init scripts for Nagios.

To make Nagios work from command line we need to install command-mode.

Next, install sample Nagios files, please run following command.

Sample output:

/usr/bin/install -c -m 775 -o nagios -g nagios -d /usr/local/nagios/etc /usr/bin/install -c -m 775 -o nagios -g nagios -d /usr/local/nagios/etc/objects /usr/bin/install -c -b -m 664 -o nagios -g nagios sample-config/nagios.cfg /usr/local/nagios/etc/nagios.cfg /usr/bin/install -c -b -m 664 -o nagios -g nagios sample-config/cgi.cfg /usr/local/nagios/etc/cgi.cfg /usr/bin/install -c -b -m 660 -o nagios -g nagios sample-config/resource.cfg /usr/local/nagios/etc/resource.cfg /usr/bin/install -c -b -m 664 -o nagios -g nagios sample-config/template-object/templates.cfg /usr/local/nagios/etc/objects/templates.cfg /usr/bin/install -c -b -m 664 -o nagios -g nagios sample-config/template-object/commands.cfg /usr/local/nagios/etc/objects/commands.cfg /usr/bin/install -c -b -m 664 -o nagios -g nagios sample-config/template-object/contacts.cfg /usr/local/nagios/etc/objects/contacts.cfg /usr/bin/install -c -b -m 664 -o nagios -g nagios sample-config/template-object/timeperiods.cfg /usr/local/nagios/etc/objects/timeperiods.cfg /usr/bin/install -c -b -m 664 -o nagios -g nagios sample-config/template-object/localhost.cfg /usr/local/nagios/etc/objects/localhost.cfg /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.

Step 5: Customizing Nagios Configuration

Open the “contacts.cfg” file with your choice of editor and set the email address associated with the nagiosadmin contact definition to receiving email alerts.

# vi /usr/local/nagios/etc/objects/contacts.cfg

Sample Output

############################################################################### ############################################################################### # # CONTACTS # ############################################################################### ############################################################################### # Just one contact defined by default - the Nagios admin (that's you) # This contact definition inherits a lot of default values from the 'generic-contact' # template which is defined elsewhere. 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 [email protected] ; *** CHANGE THIS TO YOUR EMAIL ADDRESS **** }

Step 6: Install and Configure Web Interface for Nagios

We are done with all configuration in the backend, now we will configure Web Interface For Nagios with the following command. The below command will Configure Web interface for Nagios and a web admin user will be created “nagiosadmin”.

In this step, we will be creating a password for “nagiosadmin”. After executing this command, please provide a password twice and keep it remember because this password will be used when you login in the Nagios Web interface.

[[email protected] nagios-4.4.5]# htpasswd -s -c /usr/local/nagios/etc/htpasswd.users nagiosadmin New password: Re-type new password: Adding password for user nagiosadmin

Restart Apache to make the new settings take effect.

[[email protected] nagios-4.4.5]# service httpd start [On RHEL/CentOS 6] [[email protected] nagios-4.4.5]# systemctl start httpd.service [On RHEL/CentOS 7/8 and Fedora]

Step 7: Compile and Install Nagios Plugin

We have downloaded Nagios plugins in /root/nagios, Go there and configure and install it as directed below.

Step 8: Verify Nagios Configuration Files

Now we are all done with Nagios configuration and its time to verify it and to do so please insert following command. If everything goes smooth it will show up similar to below output.

Sample Output

Nagios Core 4.4.5 Copyright (c) 2009-present Nagios Core Development Team and Community Contributors Copyright (c) 1999-2009 Ethan Galstad Last Modified: 2019-08-20 License: GPL Website: https://www.nagios.org Reading configuration data... Read main config file okay... Read object config files okay... Running pre-flight check on configuration data... Checking objects... Checked 8 services. Checked 1 hosts. Checked 1 host groups. Checked 0 service groups. Checked 1 contacts. Checked 1 contact groups. Checked 24 commands. Checked 5 time periods. Checked 0 host escalations. Checked 0 service escalations. Checking for circular paths... Checked 1 hosts Checked 0 service dependencies Checked 0 host dependencies Checked 5 timeperiods Checking global event handlers... Checking obsessive compulsive processor commands... Checking misc settings... Total Warnings: 0 Total Errors: 0 Things look okay - No serious problems were detected during the pre-flight check

Step 9: Add Nagios Services to System Startup

To make Nagios work across reboots, we need to add nagios and httpd with chkconfig and systemctl command.

On RHEL/CentOS 6

On RHEL/CentOS 7/8 and Fedora

Restart Nagios to make the new settings take effect.

[[email protected] ]# service nagios start [On RHEL/CentOS 6] [[email protected] ]# systemctl start nagios.service [On RHEL/CentOS 7/8 and Fedora]

Step 10: Login to the Nagios Web Interface

Your Nagios is ready to work, please open it in your browser with “http://Your-server-IP-address/nagios” or “http://FQDN/nagios” and Provide the username “nagiosadmin” and password.

Nagios Web Dashboard

Host View

Nagios Overview

Services View

Process View

Congratulations! You’ve successfully installed and configured Nagios and its Plugins. You’ve just started your journey into monitoring.

Upgrade Nagios 3.x to Nagios 4.4.5

If you are already running an older version of Nagios, you can upgrade it anytime. To do so, you just need to download the latest tar archive of it and configure it as shown below.

That’s it for now, in my upcoming articles, I will show you how to add Linux, Windows, Printers, Switches, and Devices to Nagios monitoring Server. If you’re having any trouble while installing, please do contact us via comments. Till then stay tuned and connected to Tecmint and don’t forget to Like and Share us to spread around.

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