For now we have installed icinga on the icinga server and now will start monitoring the available hosts and also some more case studies. In icinga there is two ways of monitoring,
- Monitor “publicly available services”
- Monitor via an agent that is installed on a remote host to collect and send data to Icinga
With the first method, publicly available services refer to services that are accessible across the local network or the Internet. Common examples include HTTP, mail, SSH, and ICMP ping. This method is useful for monitoring systems that you can’t (or don’t want to) install an agent on, and also for monitoring user facing network interfaces.
To implement the second method, we will install NRPE as an agent on remote hosts to monitor their local resources. This will allow Icinga to monitor things like disk usage, running processes, and other system stats that the first method can’t achieve.
Way1: Monitor “publicly available services”
First way is simply monitors listening services, the configuration for this method is done all on the Icinga server. Several things can be monitored with this method, so will see how to monitor a public interface of a web server.
Create a file with the name of your host, with this command (hostname with your own hostname):
# vi /etc/icinga/objects/<hostname>.cfg
Ex:
# vi /etc/icinga/objects/foxutech.cfg
You can use following by, replacing the values of host_name with your own hostname (in both places), alias with a description of the host, and address with the value of your host’s public IP address:
define host {
use                    generic-host
host_name              myweb-F
alias                  FoxuTech Web Server
address                36.54.xxx.xxx
}
define service {
use                    generic-service
host_name              myweb-F
service_description    HTTP
check_command          check_http
}
Now save and quit. Reload your Icinga configuration to put any changes into effect:
# service icinga reload
Way2: Monitor via an agent
As we discussed earlier, Icinga uses NRPE tool as an agent to collect host data for icinga. To use NRPE, it must to installed on remote hosts to monitor and also icinga server too need to configure to receive data for each other.
Installing NRPE On a Remote Host
On a host that you want to monitor, update apt
# apt-get update
Now install NRPE and Nagios Plugins
# apt-get install nagios-plugins nagios-nrpe-server
Look up the name of your var filesystem (will configure monitor for this filesystem):
# df -h /var
We need to use the filesystem name in the NRPE configuration file to monitor required filesystem disk (may probably /dev/sda). Let’s open nrpe.cfg,
# vi /etc/nagios/nrpe.cfg
To setup the monitor and sent data to server we should do config changes, it’s quite lengthy file you can file the parameter and change it your setup
- server_address: Set to the private IP address of this host
- allowed_hosts: Set to the private IP address of your Icinga server
- command[check_hda1]: Change /dev/hda1 to whatever your root filesystem is called
example:
server_address=client_private_IP
allowed_hosts=nagios_server_private_IP
command[check_hda1]=/usr/lib/nagios/plugins/check_disk -w 20% -c 10% -p /dev/sda
Note that there are several other “commands” defined in this file that will run if the Icinga server is configured to use them. Also note that NRPE will be listening on port 5666 because server_port=5666 is set. If you have any firewalls blocking that port, be sure to open it to your Icinga server.
Save and quit. Then restart NRPE to put the changes into effect:
# service nagios-nrpe-server restart
Once you are done installing and configuring NRPE on the hosts that you want to monitor, you will have to add these hosts to your Icinga server configuration before it will start monitoring them.
Add Remote Host To Icinga Server Configuration
On your Icinga server, create a new configuration file for each of the remote hosts that you want to monitor in /etc/icinga/objects. Replace yourhost with the name of your host:
# vi /etc/icinga/objects/yourhost.cfg
Add in the following host definition, replacing the host_name value with your remote hostname (I used “foxutech-1” in my example), the alias value with a description of the host, and the address value with the private IP address of the remote host,
define host {
use                    generic-host
host_name              foxuTech-web
alias                  foxutech alias site
address                192.168.xxx.xxx
}
Then add any of these service blocks for services you want to monitor. Note that the value of check_command determines what will be monitored, including status threshold values. Here are some examples that you can add to your host’s configuration file:
Ping:
define service {
use                           generic-service
host_name                      foxuTech-web
service_description            PING
check_command                  check_ping!100.0,20%!500.0,60%
}
SSH (notifications_enabled set to 0 disables notifications for a service):
define service {
use                            generic-service
host_name                      foxuTech-web
service_description            SSH
check_command                  check_ssh
notifications_enabled          0
}
Load:
define service {
use                            generic-service
host_name                      foxuTech-web
service_description            Current Load
check_command                 check_load!5.0!4.0!3.0!10.0!6.0!4.0
}
Current Users:
define service {
use                            generic-service
host_name                      foxuTech-web
service_description            Current Users
check_command                  check_users!20!50
}
Disk Space:
define service {
use                            generic-service
host_name                      foxuTech-web
service_description            Disk Space
check_command                  check_all_disks!20%!10%
}
If you’re wondering what use generic-service means, it is simply inheriting the values of a service template called “generic-service” that is defined by default.
Now save and quit. Reload your Icinga configuration to put any changes into effect:
# service icinga reload
Once you are done configuring Icinga to monitor all of your remote hosts, let’s check out the web interface
To check web interface, use <you-IP-Address>/icinga in your browser.
