How To Monitor Linux and Windows Server And Network Using Nagios

How To Monitor Linux and Windows Server And Network Using Nagios

by Vivek Gite on July 11, 2008 · 4 comments

This is a user contributed tutorial.

Nagios is free, open source host, service and network monitoring services. Nagios provides an extensible framework, that can monitor pretty much anything using plugins. Some of the items that can be monitored using Nagios plugins are listed below.

=> Disk space usage of remote Linux and Windows server
=> CPU Usage
=> Memory usage
=> Hardware Temperature
=> VPN tunnels
=> Router and Switches
=> Databases
=> Network services (DHCP, DNS, LDAP, SMTP etc.)

Nagios Configurations are very granular and managed using following three different category of configuration files:

• Nagios server and web console configuration files can be used to configure the Nagios server itself. For e.g. Use the nagios.cfg and cgi.cfg
• Resource files can be used to store user defined macros and sensitive configuration informations such as passwords.
• Object definition configuration files are used to store information about the hosts, services, commands, contacts, notification period etc.

Nagios has a web front end to display the status. Apart from getting the notification about the hosts and service status through email, SMS etc., you can also see the hosts, services, status through nagios web front end. You can project is on the NOC (Network Operation Center) to view the current status of your whole data center. You can also perform few actions on the web console such as disable and enable notification for a specific service. If you have defined the relationship between your hosts properly in the nagios configuration files, you can use the 3D display view to see a graphical representation of the whole data center visually. This also provides reporting feature where you can view the historic data such as availability of a particular service on a specific host over a period of time.

(Fig. 01 – Nagios web UI displaying status of various services on a Linux host)

Notification process on the Nagios is defined at a very granular level that it covers a wide range of possible scenarios on the notification including escalation process where a specific contact group can be notified if an issues has not been fixed after certain number of initial notifications. This is very helpful to automatically notify the management team about a critical service that was not fixed immediately.

Nagios can also be configured in a distributed setup, where datacenters from different parts of the world can be monitored using local nagios server that can report the status back to a central nagios server. This is achieved by NSCA (Nagios Service Check Acceptor) sending monitoring results from the local nagios server to the central server.

Following articles from The Geek Stuff blog, explains about everything that is required to get a jumpstart on the Nagios installation, configuration on Linux. This also explains about how to monitor Linux and Windows host.

Nagios 3.0 Jumpstart Guide For Linux – Overview, Installation and Configuration

Let us discuss the overview, installation and configuration of Nagios, a powerful open source monitoring solution for host and services.
 
I. Overview of nagios

II. 8 steps for installing nagios on Linux:

1. Download the nagios and plugins
2. Take care of the prerequisites
3. Create user and group for nagios
4. Install nagios
5. Configure the web interface
6. Compile and install nagios plugins
7. Start Nagios
8. Login to web interface

III. Configuration files overview

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I. Overview of Nagios

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Nagios is a host and service monitor tool. Following are some of the features of nagios.
 

• Monitor equipments such as servers, switches, routers, firewalls, power supply etc.
• Monitor services such as disk space, cpu usage, memory usage, temperature of the equipment, HTTP, Mail, SSH etc.
• Nagios can monitor pretty much anything. for e.g. host, services, databases, applications etc.
• Nagios has an extensible plugin interface for monitoring user defined services. There are lot of plugins available for Nagios. Visit NagiosPlugins and NagiosExchange for review the available user developed plugins.
• It can send out various notifications ( email, pager etc.) when the problem occurs and get resolved.
• Web interface to view current status, notifications, problem history, log files etc.

Following is a partial screenshot of the nagios web dashboard:

II. 8 steps for installing nagios on Linux:

1. Download the nagios and plugins

Download following files from Nagios.org and move to /home/download

• nagios-3.0.1.tar.gz
• nagios-plugins-1.4.11.tar.gz

2. Take care of the prerequisites

• Make sure apache is working on the server by verifying from browser: http://localhost
• Verify whether gcc is installed

      [root@localhost]#rpm -qa | grep gcc

      gcc-3.4.6-8

      compat-gcc-32-3.2.3-47.3

      libgcc-3.4.6-8

      compat-libgcc-296-2.96-132.7.2

      compat-gcc-32-c++-3.2.3-47.3

      gcc-c++-3.4.6-8

• Verify whether GD is installed

      [root@localhost]# rpm -qa gd

      gd-2.0.28-5.4E

3. Create user and group for nagios

[root@localhost]# useradd nagios

[root@localhost]# passwd nagios

[root@localhost]# groupadd nagcmd

[root@localhost]# usermod -G nagcmd nagios

[root@localhost]# usermod -G nagcmd apache

4. Install nagios

[root@localhost]# tar xvf nagios-3.0.1.tar.gz

[root@localhost]# cd nagios-3.0.1

[root@localhost]# ./configure --with-command-group=nagcmd

[root@localhost]# make all

[root@localhost]# make install

[root@localhost]# make install-config

[root@localhost]# make install-commandmode

Following are some additional parameters that you can pass to ./configure to customize your installation. I used only --with-command-group as shown above.

        --prefix               /opt/nagios    Where to put the Nagios files

        --with-cgiurl          /nagios/cgi-bin Web server url where the cgi's will be available

        --with-htmurl          /nagios        Web server url where nagios will be available

        --with-nagios-user     nagios         user account under which Nagios will run

        --with-nagios-group    nagios         group account under which Nagios will run

        --with-command-group   nagcmd         group account which will allow the apache user to submit

                                              commands to Nagios

At the end of the configure output, it will display a summary as shown below:

*** Configuration summary for nagios 3.0.1 05-28-2008 ***:

General Options:

-------------------------

Nagios executable:  nagios

Nagios user/group:  nagios,nagios

Command user/group:  nagios,nagcmd

Embedded Perl:  no

Event Broker:  yes

Install ${prefix}:  /usr/local/nagios

Lock file:  ${prefix}/var/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:  /bin/mail

Host OS:  linux-gnu

Web Interface Options:

------------------------

HTML URL:  http://localhost/nagios/

CGI URL:  http://localhost/nagios/cgi-bin/

Traceroute (used by WAP):  /bin/traceroute

5. Configure the web interface.

[root@localhost]# make install-webconf

[root@localhost# htpasswd -c /usr/local/nagios/etc/htpasswd.users nagiosadmin

New password:

Re-type new password:

Adding password for user nagiosadmin

6. Compile and install nagios plugins

[root@localhost]# tar xvf nagios-plugins-1.4.11.tar.gz

[root@localhost]# cd nagios-plugins-1.4.11

[root@localhost]# ./configure --with-nagios-user=nagios --with-nagios-group=nagios

[root@localhost]# make

[root@localhost]# make install

Note: On Red Hat, the ./configure command mentioned above did not work and was hanging at the when it was displaying the message: checking for redhat spopen problem… Add –enable-redhat-pthread-workaround to the ./configure command as a work-around for the above problem as shown below.

[root@localhost]# ./configure --with-nagios-user=nagios --with-nagios-group=nagios --enable-redhat-pthread-workaround

7. Start Nagios

• Add the nagios to the startup routine:

      [root@localhost]# chkconfig --add nagios

      [root@localhost]# chkconfig nagios on

• Verify to make sure there are no errors in the nagios configuration file:

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

      Total Warnings: 0

      Total Errors:   0

      Things look okay - No serious problems were detected during the pre-flight check

• Start the nagios

      [root@localhost]# service nagios start

      Starting nagios: done.

8. Login to web interface

Nagios Web URL: http://localhost/nagios/
Use the userid, password that was created from step#5 above.

III. Configuration files overview

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The first configuration to modify is to change the default value of email address in /usr/local/nagios/etc/objects/contacts.cfg file to your email address.

Following are the three major configuration files located under /usr/local/nagios/etc
 

1. nagios.cfg – This is the primary Nagios configuration file where lot of global parameters that controls the nagios can be defined.
2. cgi.cfg - This files has configuration information for nagios web interface.
3. resource.cfg – If you have to pass some sensitive information (username, password etc.) to a plugin to monitor a specific service, you can define them here. This file is readable only by nagios user and group.

Following are the other configuration files under /usr/local/nagios/etc/objects directory:
 

• contacts.cfg: All the contacts who needs to be notified should be defined here. You can specify name, email address, what type of notifications they need to receive and what is the time period this particular contact should be receiving notifications etc.
• commands.cfg – All the commands to check services are defined here. You can use $HOSTNAME$ and $HOSTADDRESS$ macro on the command execution that will substitute the corresponding hostname or host ip-address automatically.
• timeperiods.cfg – Define the timeperiods. for e.g. if you want a service to be monitored only during the business hours, define a time period called businesshours and specify the hours that you would like to monitor.
• templates.cfg – Multiple host or service definition that has similar characteristics can use a template, where all the common characteristics can be defined. Use template is a time saver.
• localhost.cfg – Defines the monitoring for the local host. This is a sample configuration file that comes with nagios installation that you can use as a baseline to define other hosts that you would like to monitor.
• printer.cfg – Sample config file for printer
• switch.cfg – Sample config file for switch
• windows.cfg – Sample config file for a windows machine