Nagios on ubuntu

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In this Scenario

We have two machines: one running Ubuntu Server 10.04, which will be used for Nagios monitoring, and another running Ubuntu 10.10, serving as a remote host to be monitored. Both machines have a minimal installation.

On the Nagios Server

1. Install Required Packages:

   root@nagios-ubuntu:~# apt-get -y install ssh php5-gd gcc make build-essential libgd2-xpm-dev libssl-dev

2. Create a User for Nagios:

   root@nagios-ubuntu:~# useradd -m nagios
   root@nagios-ubuntu:~# passwd nagios

   When a new user is created, a group with the same name is typically assigned. However, it's good practice to create a dedicated Nagios group and add the Nagios user to both this group and the www-data (Apache2) group:

   root@nagios-ubuntu:~# groupadd nagios
   root@nagios-ubuntu:~# usermod -G nagios nagios
   root@nagios-ubuntu:~# usermod -a -G nagios www-data

3. Create a Directory for Nagios Files:

   root@nagios-ubuntu:~# mkdir /garbage
   root@nagios-ubuntu:/garbage# wget http://prdownloads.sourceforge.net/sourceforge/nagios/nagios-3.3.1.tar.gz http://prdownloads.sourceforge.net/sourceforge/nagiosplug/nagios-plugins-1.4.15.tar.gz

4. Extract the Nagios Core Package:

   root@nagios-ubuntu:/garbage# tar vxzf nagios-3.3.1.tar.gz
   root@nagios-ubuntu:/garbage# cd nagios

5. Configure and Install Nagios:

   root@nagios-ubuntu:/garbage# ./configure --with-gd-lib=/usr/lib --with-gd-inc=/usr/include --with-command-group=nagcmd

   Use sed to prevent errors during the build process:

   root@nagios-ubuntu:/garbage/nagios# sed -i 's:for file in includes/rss/\*;:for file in includes/rss/\*.\*;:g' ./html/Makefile
   root@nagios-ubuntu:/garbage/nagios# sed -i 's:for file in includes/rss/extlib/\*;:for file in includes/rss/extlib/\*.\*;:g' ./html/Makefile

   Build and install Nagios:

   root@nagios-ubuntu:/garbage/nagios# make all
   root@nagios-ubuntu:/garbage/nagios# make install
   root@nagios-ubuntu:/garbage/nagios# make install-init
   root@nagios-ubuntu:/garbage/nagios# make install-config
   root@nagios-ubuntu:/garbage/nagios# make install-commandmode
   root@nagios-ubuntu:/garbage/nagios# make install-webconf

6. Check Nagios Configuration:

   root@nagios-ubuntu:/garbage/nagios# /usr/local/nagios/bin/nagios -v /usr/local/nagios/etc/nagios.cfg

7. Set Up Login for Nagios Monitoring:

   root@nagios-ubuntu:/garbage/nagios# htpasswd -c /usr/local/nagios/etc/htpasswd.users nagiosadmin

8. Reload Apache Service:

   root@nagios-ubuntu:/garbage/nagios# sudo /etc/init.d/apache2 reload

9. Ensure Nagios Starts on Reboot:

   root@nagios-ubuntu:/garbage/nagios# ln -s /etc/init.d/nagios /etc/rcS.d/S99nagios

Installing Nagios Plugins

1. Extract and Enter the Plugins Directory:

   root@nagios-ubuntu:/garbage/nagios-plugins-1.4.15# ./configure
   root@nagios-ubuntu:/garbage/nagios-plugins-1.4.15# make
   root@nagios-ubuntu:/garbage/nagios-plugins-1.4.15# make install

2. Verify Nagios Configuration Again:

   root@nagios-ubuntu:/garbage/nagios-plugins-1.4.15# /usr/local/nagios/bin/nagios -v /usr/local/nagios/etc/nagios.cfg

3. Access Nagios in Your Browser:

   Point your browser to http://Nagios_Machine's_IP/nagios.

Monitoring Linux Hosts

On the remote Ubuntu machine:

1. Install Required Packages:

   root@ubuntu:/# apt-get install libssl-dev gcc

2. Download NRPE Add-on:

   root@ubuntu:/addons# wget http://prdownloads.sourceforge.net/sourceforge/nagios/nrpe-2.13.tar.gz http://prdownloads.sourceforge.net/sourceforge/nagiosplug/nagios-plugins-1.4.15.tar.gz

3. Create a Nagios User:

   root@ubuntu:/addons# useradd nagios
   root@ubuntu:/addons# passwd nagios

4. Extract and Install Nagios Plugins:

   root@ubuntu:/addons# tar vxzf nagios-plugins-1.4.15.tar.gz
   root@ubuntu:/addons# cd nagios-plugins-1.4.15/
   root@ubuntu:/addons/nagios-plugins-1.4.15/# ./configure
   root@ubuntu:/addons/nagios-plugins-1.4.15/# make
   root@ubuntu:/addons/nagios-plugins-1.4.15/# make install

5. Extract and Install NRPE:

   root@ubuntu:/addons/nrpe-2.13# tar vxzf nrpe-2.13.tar.gz
   root@ubuntu:/addons/nrpe-2.13# cd nrpe-2.13/
   root@ubuntu:/addons/nrpe-2.13# ./configure
   root@ubuntu:/addons/nrpe-2.13# make all
   root@ubuntu:/addons/nrpe-2.13# make install-plugin
   root@ubuntu:/addons/nrpe-2.13# make install-daemon
   root@ubuntu:/addons/nrpe-2.13# make install-daemon-config

6. Run NRPE as a Service Under xinetd:

   root@ubuntu:/addons/nrpe-2.13# make install-xinetd

7. Edit the NRPE Configuration:

   Update the /etc/xinetd.d/nrpe file to include the IP address of the monitoring server:

   only_from = 127.0.0.1 192.168.56.102

8. Add NRPE Entry to /etc/services:

   nrpe 5666/tcp # NRPE

9. Restart xinetd Service:

   root@ubuntu:/addons/nrpe-2.13# service xinetd restart
           

10. Check if NRPE is Running:

    root@ubuntu:/addons/nrpe-2.13# netstat -at | grep nrpe

11. Issue Commands to Verify NRPE:

    /usr/local/nagios/libexec/check_nrpe -H localhost -c check_users
    /usr/local/nagios/libexec/check_nrpe -H localhost -c check_load

Installing NRPE on Monitoring Server

1. Extract and Install NRPE:

   root@ubuntu:/garbage/nrpe-2.13# tar vxzf nrpe-2.13.tar.gz
   root@ubuntu:/garbage/nrpe-2.13# cd nrpe-2.13/
   root@ubuntu:/garbage/nrpe-2.13# ./configure
   root@ubuntu:/garbage/nrpe-2.13# make all
   root@ubuntu:/garbage/nrpe-2.13# make install-plugin

2. Check Communication with Remote Host:

   root@ubuntu:/garbage/nrpe-2.13# /usr/local/nagios/libexec/check_nrpe -H 192.168.56.103

   If successful, you should see NRPE v2.13.

3. Configure Nagios for Remote Host Monitoring: Open the main Nagios config file:

   root@ubuntu:/usr/local/nagios/etc/objects# vim /usr/local/nagios/etc/nagios.cfg

   Update the admin_email field and add:

   cfg_file=/usr/local/nagios/etc/objects/ubuntu.cfg

4. Create Remote Host Configuration File: Create ubuntu.cfg under the same path, copying from localhost.cfg as needed. Change the ownership and update parameters:

   hostgroup_name My remote ubuntu machines
   # Change the IP and hostname accordingly

5. Reload Nagios: Restart Apache and Nagios services, then access http://your_Nagios_IP/nagios to monitor the added host.

Monitoring a Windows Client

1. Install NSClient++ on the Windows Machine: Set it to run as a service and start at boot.
2. Add Windows Object Definition in Nagios: Update nagios.cfg with:

   cfg_file=/usr/local/nagios/etc/objects/winxp.cfg

3. Create Windows Configuration File: Create winxp.cfg in the specified path, using windows.cfg as a template if needed. Update the IP and hostgroup_name accordingly.

Happy Monitoring!

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