Thursday, 12 July 2018

How to Add Linux Host to Nagios Monitoring Server Using NRPE Plugin

Nagios 4.2.0 Installation Guide on RHEL/CentOS 7.x/6.x/5.x & Fedora 24-19
How to Add Windows Host to Nagios Monitoring Server

Once you’ve installed, you can proceed further to install NRPE agent on your Remote Linux host. Before heading further, let us give you a short description about NRPE.

What is NRPE?

The NRPE (Nagios Remote Plugin Executor) plugin allows you to monitor any remote Linux/Unix services or network devices. This NRPE add-on allows Nagios to monitor any local resources like CPU load, Swap, Memory usage, Online users, etc. on remote Linux machines. After all, these local resources are not mostly exposed to external machines, an NRPE agent must be installed and configured on the remote machines.

Note: The NRPE addon requires that Nagios Plugins must be installed on the remote Linux machine. Without these, the NRPE daemon will not work and will not monitor anything.

Installation of NRPE Plugin

To use the NRPE, you will need to do some additional tasks on both the Nagios Monitoring Host and Remote Linux Host that the NRPE installed on. We will be covering both the installation parts separately.

We assume that you are installing the NRPE on a host that supports TCP wrappers and Xinted daemon installed on it. Today, most of the modern Linux distributions have these two installed by default. If not, we will install it later during the installation when required.

On Remote Linux Host

Please use the below instructions to install Nagios Plugins and NRPE daemon on the Remote Linux Host.

Step 1: Install Required Dependencies

We need to install required libraries like gcc, glibc, glibc-common and GD and its development libraries before installing.

[root@tecmint]# yum install -y gcc glibc glibc-common gd gd-devel make net-snmp openssl-devel
-------------- On Fedora 22+ Onwards --------------
[root@tecmint]# dnf install -y gcc glibc glibc-common gd gd-devel make net-snmp openssl-devel

Step 2: Create Nagios User

Create a new nagios user account and set a password.

[root@tecmint]# useradd nagios
[root@tecmint]# passwd nagios

Step 3: Install the Nagios Plugins

Create a directory for installation and all its future downloads.

[root@tecmint]# cd /root/nagios

Now download latest Nagios Plugins 2.1.2 package with wget command.

[root@tecmint nagios~]# wget https://www.nagios-plugins.org/download/nagios-plugins-2.1.2.tar.gz

Step 4: Extract Nagios Plugins

Run the following tar command to extract the source code tarball.

[root@tecmint nagios~]# tar -xvf nagios-plugins-2.1.2.tar.gz

After, extracting one new folder will appear in that directory.

[root@tecmint nagios ~]# ls -l
total 2640
drwxr-xr-x. 15 root root    4096 Aug  1 21:58 nagios-plugins-2.1.2
-rw-r--r--.  1 root root 2695301 Aug  1 21:58 nagios-plugins-2.1.2.tar.gz

Step 5: Compile and Install Nagios Plugins

Next, compile and install using following commands

[root@tecmint nagios]# cd nagios-plugins-2.1.2
[root@tecmint nagios-plugins-2.1.2]# ./configure 
[root@tecmint nagios-plugins-2.1.2]# make
[root@tecmint nagios-plugins-2.1.2]# make install

Set the permissions on the plugin directory.

[root@tecmint nagios-plugins-2.1.2]# chown nagios.nagios /usr/local/nagios
[root@tecmint nagios-plugins-2.1.2]# chown -R nagios.nagios /usr/local/nagios/libexec

Step 6: Install Xinetd

Most of the systems, its by default installed. If not, install xinetd package using following yum command.

[root@tecmint nagios-plugins-2.1.2]# yum install xinetd
-------------- On Fedora 22+ Onwards --------------
[root@tecmint nagios-plugins-2.1.2]# dnf install xinetd

Step 7: Install NRPE Plugin

Download latest NRPE Plugin 3.0 packages with wget command.

[root@tecmint nagios-plugins-2.1.2]# cd /root/nagios
[root@tecmint nagios]# wget http://liquidtelecom.dl.sourceforge.net/project/nagios/nrpe-3.x/nrpe-3.0.tar.gz

Unpack the NRPE source code tarball.

[root@tecmint nagios]# tar xzf nrpe-3.0.tar.gz
[root@tecmint nrpe-3.0]# cd nrpe-3.0

Compile and install the NRPE addon.

[root@tecmint nrpe-3.0]# ./configure
[root@tecmint nrpe-3.0]# make all

Next, install the NRPE plugin daemon, and sample daemon config file.

[root@tecmint nrpe-3.0]# make install-plugin
[root@tecmint nrpe-3.0]# make install-daemon
[root@tecmint nrpe-3.0]# make install-daemon-config

Install the NRPE daemon under xinetd as a service.

[root@tecmint nrpe-3.0]# make install-xinetd
OR
[root@tecmint nrpe-3.0]# make install-inetd

Now open /etc/xinetd.d/nrpe file and add the localhost and IP address of the Nagios Monitoring Server.

only_from = 127.0.0.1 localhost <nagios_ip_address>

Next, open /etc/services file add the following entry for the NRPE daemon at the bottom of the file.

nrpe            5666/tcp                 NRPE

Restart the xinetd service.

[root@tecmint]# service xinetd restart

Step 8: Verify NRPE Daemon Locally

Run the following command to verify the NRPE daemon working correctly under xinetd.

[root@tecmint]# netstat -at | grep nrpe
tcp        0      0 *:nrpe                      *:*                         LISTEN

If you get output similar to above, means it working correctly. If not, make sure to check the following things.

Check you’ve added nrpe entry correctly in /etc/services file
The only_from contains an entry for “nagios_ip_address” in the /etc/xinetd.d/nrpe file.
The xinetd is installed and started.
Check for the errors in the system log files for about xinetd or nrpe and fix those problems.

Next, verify the NRPE daemon is functioning properly. Run the “check_nrpe” command that was installed earlier for testing purposes.

[root@tecmint]# /usr/local/nagios/libexec/check_nrpe -H localhost

You will get a following string on the screen, it shows you what version of NRPE is installed:

NRPE v3.0

Step 9: Configure Firewall Rules

Make sure that the Firewall on the local machine will allow the NRPE daemon to be accessed from remote servers. To do this, run the following iptables command.

-------------- On RHEL/CentOS 6/5 and Fedora --------------
[root@tecmint]# iptables -A INPUT -p tcp -m tcp --dport 5666 -j ACCEPT
-------------- On RHEL/CentOS 7 and Fedora 19 Onwards --------------
[root@tecmint]# firewall-cmd --permanent --zone=public --add-port=5666/tcp

Run the following command to Save the new iptables rule so it will survive at system reboots.

-------------- On RHEL/CentOS 6/5 and Fedora --------------
[root@tecmint]# service iptables save

Step 10: Customize NRPE commands

The default NRPE configuration file that got installed has several command definitions that will be used to monitor this machine. The sample configuration file located at.

[root@tecmint]# vi /usr/local/nagios/etc/nrpe.cfg

The following are the default command definitions that are located at the bottom of the configuration file. For the time being, we assume you are using these commands. You can check them by using the following commands.

# /usr/local/nagios/libexec/check_nrpe -H localhost -c check_users
USERS OK - 1 users currently logged in |users=1;5;10;0

# /usr/local/nagios/libexec/check_nrpe -H localhost -c check_load
OK - load average: 3.90, 4.37, 3.94|load1=3.900;15.000;30.000;0; load5=4.370;10.000;25.000;0; load15=3.940;5.000;20.000;0;

# /usr/local/nagios/libexec/check_nrpe -H localhost -c check_hda1
DISK OK - free space: /boot 154 MB (84% inode=99%);| /boot=29MB;154;173;0;193

# /usr/local/nagios/libexec/check_nrpe -H localhost -c check_total_procs
PROCS CRITICAL: 297 processes

# /usr/local/nagios/libexec/check_nrpe -H localhost -c check_zombie_procs
PROCS OK: 0 processes with STATE = Z

You can edit and add new command definitions by editing the NRPE config file. Finally, you’ve successfully installed and configured NRPE agent on the Remote Linux Host. Now it’s time to install a NRPE component and add some services on your Nagios Monitoring Server…

On Nagios Monitoring Server

Now login into your Nagios Monitoring Server. Here you will need to do following things:

Install the check_nrpe plugin.
Create a Nagios command definition using the check_nrpe plugin.
Create Nagios host and add service definitions for monitoring the remote Linux host.

Step 1: Install NRPE Plugin

Go to the nagios download directory and download latest NRPE Plugin with wget command.

[root@tecmint]# cd /root/nagios
[root@tecmint]# wget http://liquidtelecom.dl.sourceforge.net/project/nagios/nrpe-3.x/nrpe-3.0.tar.gz

Unpack the NRPE source code tarball.

[root@tecmint]# tar xzf nrpe-3.0.tar.gz
[root@tecmint]# cd nrpe-3.0

Compile and install the NRPE addon.

[root@tecmint]# ./configure
[root@tecmint]# make all
[root@tecmint]# make install-daemon

Step 2: Verify NRPE Daemon Remotely

Make sure that the check_nrpe plugin can communicate with the NRPE daemon on the remote Linux host. Add the IP address in the command below with the IP address of your Remote Linux host.

[root@tecmint]# /usr/local/nagios/libexec/check_nrpe -H <remote_linux_ip_address>

You will get a string back that shows you what version of NRPE is installed on the remote host, like this:

NRPE v3.0

If your receive a plugin time-out error, then check the following things.

Make sure your firewall isn’t blocking the communication between the remote host and the monitoring host.
Make sure that the NRPE daemon is installed correctly under xinetd.
Make sure that the remote Linux host firewall rules blocking the monitoring server from communicating to the NRPE daemon.

Adding Remote Linux Host to Nagios Monitoring Server

To add a remote host you need to create a two new files “hosts.cfg” and “services.cfg” under “/usr/local/nagios/etc/” location.

[root@tecmint]# cd /usr/local/nagios/etc/
[root@tecmint]# touch hosts.cfg
[root@tecmint]# touch services.cfg

Now add these two files to main Nagios configuration file. Open nagios.cfg file with any editor.

[root@tecmint]# vi /usr/local/nagios/etc/nagios.cfg

Now add the two newly created files as shown below.

# You can specify individual object config files as shown below:
cfg_file=/usr/local/nagios/etc/hosts.cfg
cfg_file=/usr/local/nagios/etc/services.cfg

Now open hosts.cfg file and add the default host template name and define remote hosts as shown below. Make sure to replace host_name, alias and address with your remote host server details.

[root@tecmint]# vi /usr/local/nagios/etc/hosts.cfg

## Default Linux Host Template ##
define host{
name                            linux-box               ; Name of this template
use                             generic-host            ; Inherit default values
check_period                    24x7        
check_interval                  5       
retry_interval                  1       
max_check_attempts              10      
check_command                   check-host-alive
notification_period             24x7    
notification_interval           30      
notification_options            d,r     
contact_groups                  admins  
register                        0                       ; DONT REGISTER THIS - ITS A TEMPLATE
}
## Default
define host{
use                             linux-box               ; Inherit default values from a template
host_name                       tecmint          ; The name we're giving to this server
alias                           CentOS 6                ; A longer name for the server
address                         5.175.142.66            ; IP address of Remote Linux host
}

Next open services.cfg file add the following services to be monitored.

[root@tecmint]# vi /usr/local/nagios/etc/services.cfg

define service{
use                     generic-service
host_name               tecmint
service_description     CPU Load
check_command           check_nrpe!check_load
}
define service{
use                     generic-service
host_name               tecmint
service_description     Total Processes
check_command           check_nrpe!check_total_procs
}
define service{
use                     generic-service
host_name               tecmint
service_description     Current Users
check_command           check_nrpe!check_users
}
define service{
use                     generic-service
host_name               tecmint
service_description     SSH Monitoring
check_command           check_nrpe!check_ssh
}
define service{
use                     generic-service
host_name               tecmint
service_description     FTP Monitoring
check_command           check_nrpe!check_ftp
}

Now NRPE command definition needs to be created in commands.cfg file.

[root@tecmint]# vi /usr/local/nagios/etc/objects/commands.cfg

Add the following NRPE command definition at the bottom of the file.

###############################################################################
# NRPE CHECK COMMAND
#
# Command to use NRPE to check remote host systems
###############################################################################
define command{
command_name check_nrpe
command_line $USER1$/check_nrpe -H $HOSTADDRESS$ -c $ARG1$
}

Finally, verify Nagios Configuration files for any errors.

[root@tecmint]# /usr/local/nagios/bin/nagios -v /usr/local/nagios/etc/nagios.cfg
Total Warnings: 0
Total Errors:   0

Restart Nagios:

[root@tecmint]# service nagios restart

That’s it. Now go to Nagios Monitoring Web interface at “http://Your-server-IP-address/nagios” or “http://FQDN/nagios” and Provide the username “nagiosadmin” and password. Check that the Remote Linux Host was added and is being monitored.

Nagios Remote Host Monitoring

How to Install Nagios 4.3.4 on RHEL, CentOS and Fedora

Nagios is an awesome Open Source monitoring tool, its provides you more comprehensive monitoring environment to always keep an eye on your all machines / networks whether you are in a 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 4.3.4 and its latest stable release of Nagios plugins 2.2.1 on April 19, 2017.

This article is intended to guide you with easy instructions on how to install latest Nagios Core 4.3.4 from source (tarball) on RHEL 7.x/6.x/5.x, CentOS 7.x/6.x/5.x and Fedora 26-20 distributions.

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

Please Note: The installation instructions were shown in here are written based on CentOS 7.2 Linux distribution.

Installing Nagios 4.3.4 and Nagios Plugin 2.2.1

If you follow these instructions correctly, you will end up with 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 4.3.4 with source. And to do so, we can use yum default package installer.

[root@tecmint]# yum install -y httpd httpd-tools php gcc glibc glibc-common gd gd-devel make net-snmp
-------------- On Fedora 22+ Onwards -------------- 
[root@tecmint]# 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 and nagcmd group account and set a password.

[root@tecmint]# useradd nagios
[root@tecmint]# groupadd nagcmd

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

[root@tecmint]# usermod -G nagcmd nagios
[root@tecmint]# usermod -G nagcmd apache

Step 3: Download Nagios Core 4.3.4 and Nagios Plugin 2.2.1

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

[root@tecmint]# mkdir /root/nagios
[root@tecmint]# cd /root/nagios

Now download latest Nagios Core 4.3.4 and Nagios plugins 2.2.1 packages with wget command.

[root@tecmint nagios~]# wget https://assets.nagios.com/downloads/nagioscore/releases/nagios-4.3.4.tar.gz
[root@tecmint nagios~]# wget https://nagios-plugins.org/download/nagios-plugins-2.2.1.tar.gz

Step 4: Extract Nagios Core and its Plugins

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

[root@tecmint nagios~]# tar -xvf nagios-4.3.4.tar.gz
[root@tecmint nagios~]# tar -xvf nagios-plugins-2.2.1.tar.gz

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

[root@tecmint nagios ~]# ls -l
total 13520
drwxrwxr-x 18 root root     4096 Aug 24 17:43 nagios-4.3.4
-rw-r--r--  1 root root 11101966 Aug 24 17:48 nagios-4.3.4.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.

[root@tecmint nagios~]# cd nagios-4.3.4/
[root@tecmint nagios-4.3.4 ]# ./configure --with-command-group=nagcmd

Sample output:

Creating sample config files in sample-config/ ...
*** Configuration summary for nagios 4.3.4 2017-08-24 ***:
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:  ${prefix}/var/spool/checkresults
Init directory:  /etc/rc.d/init.d
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.

[root@tecmint nagios-4.3.4 ]# make all
[root@tecmint nagios-4.3.4 ]# make install

Sample output:

*** Exfoliation theme installed ***
NOTE: Use 'make install-classicui' to revert to classic Nagios theme
make[1]: Leaving directory `/root/nagios/nagios-4.3.4'
make install-basic
make[1]: Entering directory `/root/nagios/nagios-4.3.4'
/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 nagcmd -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 /etc/rc.d/init.d
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/nagios/nagios-4.3.4'

Following command will install the init scripts for Nagios.

[root@tecmint nagios-4.3.4 ]# make install-init

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

[root@tecmint nagios-4.3.4 ]# make install-commandmode

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

[root@tecmint nagios-4.3.4 ]# make install-config

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                           admin@tecmint.com     ; *** 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 following command. The below command will Configure Web interface for Nagios and a web admin user will be created “nagiosadmin”.

[root@tecmint nagios-4.3.4 ]# make install-webconf

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.

[root@tecmint nagios-4.3.4]# 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.

[root@tecmint ]# service httpd start               [On RHEL/CentOS 6/5 and Fedora]
[root@tecmint ]# systemctl start httpd.service     [On RHEL/CentOS 7 and Fedora 19 Onwards]

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.

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

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.

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

Sample Output

Nagios Core 4.3.4
Copyright (c) 2009-present Nagios Core Development Team and Community Contributors
Copyright (c) 1999-2009 Ethan Galstad
Last Modified: 2017-08-24
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 systemctlcommand.

On RHEL/CentOS 6/5 and Fedora

[root@tecmint ]# chkconfig --add nagios
[root@tecmint ]# chkconfig --level 35 nagios on
[root@tecmint ]# chkconfig --add httpd
[root@tecmint ]# chkconfig --level 35 httpd on

On RHEL/CentOS 7 and Fedora 19-26

[root@tecmint ]# systemctl enable nagios
[root@tecmint ]# systemctl enable httpd

Restart Nagios to make the new settings take effect.

[root@tecmint ]# service nagios start              [On RHEL/CentOS 6/5 and Fedora]
[root@tecmint ]# systemctl start nagios.service    [On RHEL/CentOS 7 and Fedora 19-24]

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

Nagios Core Running on CentOS 7.2

Host View

Nagios Host View

Nagios Overview

Nagios Monitoring Overview

Service View

Nagios Hos Services Monitoring

Process View

Nagios Core Process Information

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

Upgrade Nagios 3.x to Nagios 4.3.4

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.

[root@tecmint ]# service nagios stop
[root@tecmint ]# wget https://assets.nagios.com/downloads/nagioscore/releases/nagios-4.3.4.tar.gz
[root@tecmint ]# tar -zxvf nagios-4.3.4.tar.gz
[root@tecmint ]# cd nagios-4.3.4
[root@tecmint ]# ./configure
[root@tecmint ]# make all
[root@tecmint ]# make install
[root@tecmint ]# service nagios start