Server monitoring with icinga

What is Icinga?
From the website, icinga.org,
 "Icinga is an enterprise grade open source monitoring system which keeps watch over networks and any conceivable network resource, notifies the user of errors and recoveries and generates performance data for reporting"

If you are familiar with nagios, then you will most likely feel comfortable with icinga. Actually, icinga is a fork of nagios and uses its plugins for achieving many of its tasks.This system provides a very nice interface for monitoring systems and services on your network.

Installation and setup:
Installation will more than likely go smoothly if you can follow the instructions from icinga's documentation/quick start guide. I beleive there are packages for icinga in the debian/ubuntu repositories, so you can probably install by doing, apt-get install icinga. However, I installed it from it's sources by following the quickstart guide here.

NOTE: If you decide to create a different user other than icingaadmin from the command:

htpasswd -c /usr/local/icinga/etc/htpasswd.users icingaadmin

 , you may run into minor set backs like i did. When i logged into the web interface with the unique username i created, i was unable to see the default localhost system being monitored. To get things working, i had to modify some files, and basically add my username to certain config directives so i have the relevant permissions to view/retrieve information. Specifically, the cgi.cfg config file in the icinga's etc directory. Below are the directives that i modified. Note that the user icingaadmin is there by default, so i only appended my username.

authorized_for_system_information=icingaadmin,myusername

authorized_for_all_services=icingaadmin,myusername

authorized_for_all_hosts=icingaadmin,myusername

authorized_for_all_service_commands=icingaadmin,myusername

authorized_for_all_host_commands=icingaadmin,myusername

To add remote hosts to be monitored is also simple. I encourage you to read up on this post at howtoforge.com

Basically, if we wanted to add a system to be monitored that will only check for the system being up/alive (ping checks), we can create a config file for this host in the icinga's etc/modules directory. For example, we can name the file dhcp_server.cfg (files must end in .cfg extension).

Here is a sample of the config file contents for a simple ping host check.

define hostgroup{
     hostgroup_name     windows-machines
     alias                         window machines
     members                  dhcp_server
}

define host{
     use                           windows-server
     host_name               dhcp_server
     alias                         dhcp server
     address                     192.168.1.2
     hostgroups                windows-machines
}

define service{
     use                            generic-service
     host_name                dhcp_server
     service_description ping host
     check_command      check_ping!100.0,20%!500.0,60%
}

Save this file the restart the icinga daemon: service icinga restart. If there are no errors all should be well. Log into the web interface and confirm that your new host is being monitored. If the host at 192.168.1.2 is down, then icinga's web interface will indicate so with the red color. The green color indicates that the host is up.

Resources/Good Reading:
www.icinga.org
howtoforge.com icinga article