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Monitoring Linux Using NCPA


This article covers how to go about setting up monitoring in Linux using NCPA. You will learn how to configure NCPA to monitor Linux.

NCPA is a cross-platform monitoring agent for Nagios Core and Nagios XI that runs on Windows, Linux/Unix, and Mac OS/X machines. Its features include both active and passive checks, remote management, and a local monitoring interface.


In Nagios XI wizards can be used to to perform configuration of hosts and services through the Web UI. Wizards take the complicated matter of creating hosts and services, defining configuration parameters, assigning contacts, contact groups, hostgroups, servicegroups, etc, into a easy steps form in the Nagios XI UI. 

Wizards can also be easily added to Nagios XI through the Admin -> Manage Wizards menu to expand the capabilities of Nagios XI.

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Nagios – Monitor hosts using SSH: How to use the plugin ?


This article covers how to monitor Nagios using SSH. 

In order to monitor Linux hosts using the Nagios check_by_ssh plugin, there are a few prerequisites that must be met:

  • Create a Nagios user for monitoring on the host to be monitored.
  • Configure passwordless SSH authentication as nagios user on host to monitor.
  • Install Nagios plugins on the host to monitor.


To Create a Nagios user:

Login to the host to monitor and create a user called nagios and set the login password.

useradd -m nagios
passwd nagios

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NRPE Command Plugin Not Defined - How to fix it ?


This article covers methods to resolve 'NRPE Command Plugin Not Defined' for our customers.

This error is very straight forward. Usually this is caused by a mismatch between the command name declared in Nagios XI to be check through NRPE and the actual command name of the command directive in the remote host's nrpe.cfg file.

This problem will occur in versions of check_nrpe before v3. 

What is happening here is that the initial -c check_users is being overwritten by the -a -w 5 -c 10, as check_nrpe thinks the -c 10 argument is the command argument, not one of the -a arguments.

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NRPE: No Output Returned From Plugin - How to fix this Nagios error ?


This article covers how to resolve Nagios error, NRPE: No Output Returned From Plugin. This error happens as a result of Permissions or Missing plugin.

To fix this Nagios error:

1. The most common solution is to check the permissions on the check_nrpe binary on the Nagios XI server:

ls -la /usr/local/nagios/libexec/check_nrpe

The expected permissions should resemble:

-rwxrwxr-x. 1 nagios nagios  75444 Nov 21 01:38 check_nrpe

2. If not, change ownership to user/group "nagios" and fix up the permissions:

$ chown nagios:nagios /usr/local/nagios/libexec/check_nrpe
$ chmod u+rwx /usr/local/nagios/libexec/check_nrpe
$ chmod u+rx /usr/local/nagios/libexec/check_nrpe

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Nagios error Service check timed out after n Seconds


This article covers how to resolve 'Service check timed out after n Seconds' error for our customers.

You can increase the timeout on the check, though you will have to alter the check in XI and the plugin timeout in the ncpa.cfg file on the remote host.


If it is related to Nagios XI check_xi_ncpa Timeout:

This timeout is how long the check_xi_ncpa command on the Nagios XI server will wait for a response from the NCPA agent. 

By default the timeout is not set, thereby defaulting to the plugin timeout or the global timeout.

1. In the Nagios XI web interface navigate to Configure > Core Config Manager > Commands. 

2. This brings up the Commands page, use the Search field to search for ncpa and click Search.

3. Click the check_xi_ncpa command.

4. You can change the timeout in Nagios XI with the switch -T in the check_xi_ncpa command.

5. In the Command Line, add -T <time value in seconds> after $HOSTADDRESS$. Ex. -T 120

6. Save your changes and then click the Apply Configuration button.

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Monitoring Performance Counters in Nagios XI Using NCPA


This article will guide you on how to configure #Nagios XI to monitor performance counters by monitoring Performance Counters in Nagios XI is possible using #NCPA as well as use cases where real-time monitoring actually provides no benefit at all, and may also be both a distraction and a detriment to monitoring #teams and #admins.

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