NagiosUserManual

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Nagios User Manual

Nagios PrerequisitesBefore installing Nagios, make sure you have the following installed: Apache, PHP, GCC

compiler and GD development libraries.

Installing and Configuring NagiosNote: This Nagios installation part only monitors the services running on the monitoring

server or the localhost.

Terms:

Monitoring Server - the Virtual Server where Nagios, Nagios plug-ins and NRPE

daemon are installed.

Remote Server - the Virtual Servers being monitored by the Monitoring Server where

Nagios plug-ins and NRPE daemon are installed.

1. Create the user account nagios:

# /usr/sbin/useradd -m nagios

#passwd nagios

2. Create the group nagcmd and then add both the nagios and apache

users to this group:

# /usr/sbin/groupadd nagcmd

# /usr/sbin/usermod -a -G nagcmd nagios# /usr/sbin/usermod -a -G nagcmd apache

Note: If you encounter an error stating “user apache does not exist”, just add apache to the user

accounts.

# /usr/sbin/useradd -m apache

3. Create a directory named ‘downloads’. Cd to that directory (cd downloads), then download

Nagios and Nagios plug-ins from http://www.nagios.org/download/.

4. Extract the source code from the compressed tarball. Make sure you are in the directory

where you downloaded the source code. Note: Check the latest version in Nagios main site.

#tar xvzf nagios-3.2.0.tar.gz

#cd nagios-3.2.0

5. Run the configure script.

#./configure --with-command-group=nagcmd

6. Compile Nagio's source code.

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#make all

7. Install the binaries, init script, sample configuration files, and configure permissions before

starting Nagios:

#make install

#make install-init#make install-config

#make install-commandmode

8. Edit the configuration file that will dictate which email address will receive alerts. Enter your

email address.

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

9. Configure web interface.

#make install-webconf

10. Create the user account nagiosadmin for logging into the web interface for Nagios.

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

11. Restart the web server (httpd) (apache) web service running on the virtual server:

#service httpd restart

or

#service apache2 restart

12. Compile and install the Nagios plug-ins. Make sure you are in the directory where you

downloaded the source code. Note: Check the latest version in Nagios main site.

#tar xvzf nagios-plugins-1.4.11.tar.gz #cd nagios-plugins-1.4.11

13. Compile and install plug-ins.

#./configure --with-nagios-user=nagios --with-nagios-group=nagios

#make

#make install

14. Verify if Nagios is installed correctly and will start without error:

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

15. If no errors are reported, start Nagios:

#service nagios start

16. Test Nagios by logging into the web interface. From a remote machine, using the browser,

enter http://<ip_address_of_server>/nagios

Enter screenshot of Nagios here:

http://www.google.com/url?q=http%3A%2F%2Fserver_name%2Fnagios&sa=D&sntz=1&usg=AFQjCNEPhpzDhhlLc31nKBjw5tIHvIFLRg














Monitoring Remote Hosts using Nagios and NRPE

As we have stated before, the following installations and configurations given above is enough

to monitory only one server. If we want to monitor multiple servers in a single web interface,

we have to install the nagios plug-ins and NRPE daemon on the remote servers we want to

monitor.

Note: Make sure that necessary prerequisites stated above are installed.

On the Remote Server (the other servers you want to monitor):

1. Create a nagios user account.

#useradd nagios

#passwd nagios

2. Create a directory named ‘downloads’. Cd to that directory (cd downloads), then download

and install Nagios plug-ins. Download it from http://www.nagios.org/download/.

3. Extract the Nagios plugins. Note: Check the latest version in Nagios main site.

#tar xvzf nagios-plugins-1.4.14.tar.gz

#cd nagios-plugins-1.4.14

4.Configure and install the nagios-plugins. Make sure you are in the directory where you

downloaded the source code.

#./configure --with-nagios-user=nagios --with-nagios-group=nagios

# make

# make install

5. Change the permissions on the plugins directory:

# chown nagios.nagios /usr/local/nagios

# chown -R nagios.nagios /usr/local/nagios/libexec

6. Download and extract NRPE. Note: Make sure you are in the ‘downloads’ directory.

Download NRPE from http://www.nagios.org/download/.

# tar -xvzf nrpe-2.12.tar.gz# cd nrpe-2.12

7. Install and configure NRPE:

# ./configure

# make all

# make install-plugin

























# make install-daemon

# make install-daemon-config

# make install-xinetd

8. Configure NRPE by editing the /etc/xinetd.d/nrpe file to allow our remote server to

communicate with the monitoring server #nano vi /etc/xinetd.d/nrpe

only_from = 127.0.0.1 <insert_monitoring_server_ip> <insert_remote_server_ip>

9. Add an entry in the /etc/services file for port TCP port 5666 for NRPE to communicate.

#nano /etc/services

Add the following entry.

nrpe 5666/tcp # NRPE

10. Restart NRPE.

# service xinetd restart

11. Test if NRPE is running and listening. Run the following.

# netstat -at | grep nrpe

This must output:

tcp 0 0 *:nrpe *:* LISTEN

12. Test if the NRPE daemon is accepting connections. Run the following command:

# /usr/local/nagios/libexec/check_nrpe -H localhost

This must output:

NRPE v2.12

On the Monitoring Server:

14. Cd to the ‘downloads’’ directory. Download and extract NRPE. Download NRPE from http://

www.nagios.org/download/. Note: Check the latest version in Nagios main site.

# tar -xzf nrpe-2.12.tar.gz

# cd nrpe-2.12

15. Compile and configure NRPE:

# ./configure

# make all

# make install-plugin

16. Make sure that the NRPE plugin running on the monitoring server that performs the

monitoring can communicate with the remote host that we want to monitor:

# /usr/local/nagios/libexec/check_nrpe -H <insert_ip_of_remote_server>

This must output:

NRPE v2.12















17. Configure Nagios to use the NRPE plug in by adding in the entry below.

# nano /usr/local/nagios/etc/objects/commands.cfg

#########################################################

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 $ARG1$

}

18. Configure Nagios, using the NRPE plugin, to communicate with the remote host.

Create a template called linux-box-remote.cfg. Note: You can change the name of the

template.

# nano /usr/local/nagios/etc/objects/linux-box-remote.cfg

define host{

name linux-box-remote

use generic-host

check_period 24x7

check_interval 5

retry_interval 1

max_check_attempts 10check_command check-host-alive

notification_period 24x7

notification_options d,r

contact_groups admins

register 0

}

define host{

use linux-box-remote

host_name <any_name>

alias <change_to_any_hostname>

address <insert_remote_server_ip>

}

define service{

use generic-service


service_description CPU Load



check_command check_nrpe!check_load

}

define service{

use generic-service


service_description Current Userscheck_command check_nrpe!check_users

}

define service{

use generic-service


service_description /dev/<paritition_name> Free Space

check_command check_nrpe!check_<partition_name>

}

define service{

use generic-service


service_description Total Processes

check_command check_nrpe!check_total_procs

}

define service{

use generic-service


service_description Zombie Processes

check_command check_nrpe!check_zombie_procs

}

19. Activate the new template.

#nano /usr/local/nagios/etc/nagios.cfg

Add the following entry.

# Definitions for monitoring remote machines

cfg_file=/usr/local/nagios/etc/objects/linux-box-remote.cfg

20. Restart Nagios.

# service nagios restart

22. Verify if you can view the statistics of both servers (monitoring server and remote

server). Log-in to the web interface of a remote machine. On the browser enter http://

<ip_address_of_server>/nagios

<Enter Screenshot here>:

Monitoring Other Services

















If you want to monitor other services running on the remote servers, you can do the following:

1. On the Remote Server that is being monitored, add the proper check command for the

service. Note: You can refer the official Nagios documentation for this.

#nano /usr/local/nagios/etc/nrpe.cfg

Example:

command[check_smbd]=/usr/local/nagios/libexec/check_procs -c 1:30 -C smbd

2. On the Monitoring Server, edit the template. In this example, that template is named linux-

box-remote.cfg. Add a service definition for each service that you added in the remote server's

nrpe.cfg file. Note: You can refer the official Nagios documentation for this.

#nano /usr/local/nagios/etc/objects/linux-box-remote.cfg

Example service definition:

define service{

use generic-service

host_name <name_of_host>

service_description CHECK_SMBD

check_command check_nrpe!check_smbd

}

3. Restart Nagios.

#service nagios restart

Reference:http://lancrossdata.com/index.php?option=com_content&view=article&id=91:monitoring-linux-

with-nagios&catid=52:monitoring-linux-&Itemid=69

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NagiosUserManual