NRPE - UNKNOWN: No Handler For That Command

Problem Description

This KB article addresses the following NRPE error or variants of this error:

UNKNOWN: No Handler For That Command
No handler for command:
Unknown command(s):

Assumed Knowledge

The following KB article contains an explanation of how NRPE works and may need to be referenced to completely understand the problem and solution that is provided here:

NRPE - Agent and Plugin Explained

In addition to this, NSClient++ must be correctly installed and configured, please refer to the following KB article on enabling the NRPE listener in NSClient++:

Documentation - Enabling The NRPE Listener In NSClient++ 0.4.x

Troubleshooting The Error

This is usually caused by a missing or incorrectly spelled handler (external alias) in the remote host's C:\Program Files\NSClient++\nsclient.ini file.

Check the spelling of the check_nrpe command for the service check in Nagios XI (the name of the command after the "-c").  It should match the spelling of the external alias in the nsclient config file.  For example:

[/settings/external scripts/alias]
alias_cpu = checkCPU warn=80 crit=90 time=5m time=1m time=30s

 

In the example above, the "alias_cpu" is the handler and therefore the service check in Nagios XI should specify the check_nrpe command as "alias_cpu".

Final Thoughts

For any support related questions please visit the Nagios Support Forums at:

http://support.nagios.com/forum/