Nagios
Nagios is an open source and free computer-software application can be used to monitor systems, networks, and infrastructure. Nagios offers to monitor and alerting services for servers, switches, applications, and services. It alerts users when things go wrong and alert them a second time after the problem has been resolved.Network Monitoring
When it comes to open source network monitoring tools, the World’s largest organizations turn to Nagios. Nagios monitors the network for problems caused by overloaded data links or network connections, as well as monitoring routers, switches and more. Easily able to monitor availability, uptime and response time of every node on the network, Nagios can deliver the results in a variety of visual representations and reports.
Server Monitoring
Nagios is known for being the best server monitoring software on the market. Server monitoring is made easy in Nagios because of the flexibility to monitor your servers with both agent-based and agentless monitoring. With over 5000 different add-ons available to monitor your servers, the community at the Nagios Exchange have left no stone unturned.
Application Monitoring
Implementing effective application monitoring with Nagios allows your organization to quickly detect application, service, or process problems, and take action to eliminate downtime for your application users. Nagios provides tools for monitoring of applications and application state – including Windows applications, Linux applications, UNIX applications, and Web applications.
Prerequisites
To follow this tutorial, you must have superuser privileges on the Ubuntu 14.04 server that will run Nagios. Ideally, you will be using a non-root user with superuser privileges.
LAMP Stack Script
Nagios runs on LAMP stack which can be installed by below mentioned script.
$ cat lampstack.sh
apt-get update
apt-get install apache2 mysql-server php5-mysql vim php5 libapache2-mod-php5 php5-mcrypt
sudo mysql_install_db
sudo mysql_secure_installation
echo -e "<'IfModule mod_dir.c>\n DirectoryIndex index.php index.html index.cgi index.pl index.xhtml index.htm\n<'/IfModule>" > /etc/apache2/mods-enabled/dir.conf
service apache2 restart
apt-get install php5-cli
LAMP stack is also required.
NAGIOS SETUP
Create the Nagios user and group
Create a Nagios user and a group.
sudo add user nagios
sudo add group nagcmd
sudo user-mod –a –G nagcmd nagios
Install the dependencies
First, update your apt-get package lists:
sudo apt-get update
Let’s install all the dependencies we will need to install Nagios with this command sudo apt-get install build-essential libgd2-xpm-dev openssl libssl-dev xinetd apache2-utils unzip apache2-utils, which will be used to set up the Nagios web interface.
As we are building the nagios core from the source, we should need all these libraries to be installed.
Install Nagios core
For installing we have placed all the commands together and made as a script Vi naginstall.sh
# move to the home directory
cd ~
#Download the Nagios tar file from this URL
curl -L -O https://assets.nagios.com/downloads/nagioscore/releases/nagios-4.1.1.tar.gz
#Extract the Nagios archive with this command:
tar xvf nagios-*.tar.gz
#Then change to the extracted directory:
cd nagios-*
#Before building Nagios, we must configure it.
./configure --with-nagios-group=nagios --with-command-group=nagcmd --with-mail=/usr/sbin/sendmail
#Now compile Nagios with this command:
make all
#Now we can run these make commands below to build and install Nagios, init scripts, and sample configuration
files:
sudo make install
sudo make install-commandmode
sudo make install-init
sudo make install-config
sudo /usr/bin/install -c -m 644 sample-config/httpd.conf /etc/apache2/sites-available
#To issue external commands via the web interface to Nagios, we must add the web server user, www-data, to the nagcmd group:
sudo usermod -G nagcmd www-data
Execute the above script to install nagios core
#./ naginstall.sh
Install the Nagios Plugins
Vi npinstall.sh#move to user’s home directory
cd ~
#download the tar file for the Nagios plugins using the command
curl -L -O http://nagios-plugins.org/download/nagios-plugins-2.1.1.tar.gz
#Extract Nagios Plugins archive with this command:
tar xvf nagios-plugins-*.tar.gz
#Then change to the extracted directory:
cd nagios-plugins-*
#Before building Nagios Plugins, we must configure it. Use this command:
./configure --with-nagios-user=nagios --with-nagios-group=nagios --with-openssl
#Now compile Nagios Plugins with this command:
Make
#Then install it with this command:
sudo make install
Execute the above script to complete the installation with the nagios plugins
#./ npinstall.sh
Install NRPE
Find the source code for the latest stable release of NRPE at the NRPE downloads page. Download the latest version to your Nagios server.
At the time of this writing, the latest release is 2.15.:
Vi nrpeinstall.sh
#move to the home directory for the user
cd ~
#download the tar file to our home directory with curl
curl -L -O http://downloads.sourceforge.net/project/nagios/nrpe-2.x/nrpe-2.15/nrpe-2.15.tar.gz
#Extract the NRPE archive with this command:
tar xvf nrpe-*.tar.gz
#Then change to the extracted directory:
cd nrpe-*
#Configure NRPE with these commands:
./configure --enable-command-args --with-nagios-user=nagios --with-nagios-group=nagios --with-ssl=/usr/bin/openssl --with-ssl-lib=/usr/lib/x86_64-linux-gnu
#Now build and install NRPE and its xinetd startup script with these commands:
make all
sudo make install
sudo make install-xinetd
sudo make install-daemon-config
Now open the xinetd startup script in an editor:
sudo vi /etc/xinetd.d/nrpe
In the file modify the only_from line by adding the private IP address of the your Nagios server to the end (substitute in the actual IP address of your server):
only_from = 127.0.0.1 192.168.1.20
Restart the xinetd service to start NRPE:
sudo service xinetd restart
Configure Nagios
Open the Nagios configuration file:
sudo vi /usr/local/nagios/etc/nagios.cfg
#cfg_dir=/usr/local/nagios/etc/servers
#cfg_dir=/usr/local/nagios/etc/printers
#cfg_dir=/usr/local/nagios/etc/switches
#cfg_dir=/usr/local/nagios/etc/routers
Uncomment all the devices you will be monitoring, and save the file.
Now create the directories for all the devices you will be monitoring in each of those paths above: for example type sudo mkdir /usr/local/nagios/etc/servers for the servers.
Configure Nagios Contacts
In order to receive notifications from Nagios you need to configure the contacts. open the contact configuration file, and add the email address you want to receive the emails from Nagios.
Find the email directive, and replace its value nagios@localhost with our own email address nagiosadmin@gmail.com ( Taken Randomly)
sudo vi /usr/local/nagios/etc/objects/contacts.cfg email nagios@localhost ; <<***** CHANGE THIS TO YOUR EMAIL ADDRESS ******
Configure the NRPE command
Open the command configuration file sudo nano /usr/local/nagios/etc/objects/commands.cfg and add the following command at the end of the file:
define command {
command_name check_nrpe
command_line $USER1$/check_nrpe -H $HOSTADDRESS$ -c $ARG1$ }
Configure Apache
Enable mod_rewrite
sudo a2enmod rewrite
enable the CGI module
sudo a2enmod cgi
Create the default Nagios account to login to the Nagios using this command,
sudo htpasswd -c /usr/local/nagios/etc/htpasswd.users nagiosadmin
enter the password when prompted:
Create a symbolic link from the nagios.conf file to the apache enabled sites:
sudo ln -s /etc/apache2/sites-available/nagios.conf /etc/apache2/sites-enabled/
Start Nagios and restart Apache
sudo service nagios start
sudo service apache2 restart
To start Nagios at every server reboot, create this symbolic link
sudo ln -s /etc/init.d/nagios /etc/rcS.d/S99nagios
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