check_disk not generating alerts: nagios - monitoring

Question

I am new to nagios.
I am trying to configure the "check_disk" service for one host but I am not getting the expected results.
I should get the emails when when disk usage goes beyond 80%.
So, There is already service defined for this task with multiple hosts, as below:
define service{
use local-service ; Name of service template to use
host_name localhost, host1, host2, host3, host4, host5, host6
service_description Root Partition
check_command check_local_disk!20%!10%!/
contact_groups unix-admins,db-admins
}
The Issue:
Further I tried to test single host i.e. "host2". The current usage of host2 is as follow:
# df -h /
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/rootvg-rootvol 94G 45G 45G 50% /
So to get instant emails, I written another service as below, where warning set to <60% and critical set to <40%.
define service{
use local-service
host_name host2
service_description Root Partition again
check_command check_local_disk!60%!40%!/
contact_groups dev-admins
}
But still I am not receive any emails for the same.
Where it going wrong.
The "check_local_disk" command is defined as below:
define command{
command_name check_local_disk
command_line $USER1$/check_disk -w $ARG1$ -c $ARG2$ -p $ARG3$
}

Answer 1

Your command definition currently is setup to only check your Nagios server's disk, not the remote hosts (such as host2). You need to define a new command definition to execute check_disk on the remote host via NRPE (Nagios Remote Plugin Execution).
On Nagios server, define the following:
define command {
command_name check_remote_disk
command_line $USER1$/check_nrpe -H $HOSTADDRESS$ -c check_disk -a $ARG1$ $ARG2$ $ARG3$
register 1
}
define service{
use genric-service
host_name host1, host2, host3, host4, host5, host6
service_description Root Partition
check_command check_remote_disk!20%!10%!/
contact_groups unix-admins,db-admins
}
Restart the Nagios service.
On the remote host:
Ensure you have NRPE plugin installed.
Instructions for Ubuntu: http://tecadmin.net/install-nrpe-on-ubuntu/
Instructions for CentOS / RHEL: http://sharadchhetri.com/2013/03/02/how-to-install-and-configure-nagios-nrpe-in-centos-and-red-hat/
Ensure there is a command defined for check_disk on the remote host. This is usually included in nrpe.cfg, but commented-out. You'd have to un-comment the line.
Ensure you have the check_disk plugin installed on the remote host. Mine is located at: /usr/lib64/nagios/plugins/check_disk
Ensure that allowed_hosts field of nrpe.cfg includes the IP address / hostname of your Nagios server.
Ensure that dont_blame_nrpe field of nrpe.cfg is set to 1 to allow command line arguments to NRPE commands: dont_blame_nrpe=1
If you made any changes, restart the nrpe service.