Why am i getting “NRPE: Unable to read output”?
Usually this is a configuration error on Nagios client side. It is a problem in check command definition in “nrpe.cfg” file on Nagios client. If you see this error you probably defined a check command calling a Nagios Plugin file which does not exist.
UPDATE: If you installed your NRPE client from RPM, nrpe.cgf file is located at /etc/nagios/nrpe.cfg.
How to fix “NRPE: Unable to read output” error?
1. Check configuration
First check Nagios service configuration for “CLUSTER state” on the server side:
define service{
use geek-service
host_name foo1.geekpeek.net
service_description CLUSTER state
check_command check_nrpe!check_cluster
contact_groups geek-admin
}“check_command” line tells us we must find “check_cluster” command definition on Nagios client!
2. Find command definition
Next find “check_cluster“ command definition in “nrpe.cfg” on the Nagios client side:
... command[check_cluster]=/usr/lib64/nagios/plugins/check_crmd ...
3. Run command
Manually run defined “check_crmd” command on Nagios client:
[root@fooclient ~]# /usr/lib64/nagios/plugins/check_crmd -bash: /usr/lib64/nagios/plugins/check_crmd: No such file or directory
Clearly “check_crmd” file is missing.
4. Run fixed
Correct the “check_cluster” definition by calling the correct Nagios plugin file (in our case /usr/lib64/nagios/plugins/check_crm) and manually run command again:
[root@fooclient ~]# /usr/lib64/nagios/plugins/check_crm check_crm OK - Cluster OK
Great this solved it!
5. Edit nrpe.cfg
Edit “nrpe.cfg” file to run the correct Nagios plugin
... command[check_cluster]=/usr/lib64/nagios/plugins/check_crm ...
6. Restart NRPE service
Restart NRPE service on Nagios client for changes to take effect!
In our case the problem was a spelling mistake when configuring NRPE service on Nagios client, but sometimes this kind of problem can arise from a missing Nagios plugin installation. If you are missing a Nagios plugin you will need to find it and install it.
Also make sure to make manual service checks by running the plugins locally on your Nagios client machine. It is always wise to first make manual checks on Nagios client and next manual checks from Nagios server. In the end you can edit the NRPE configuration file and restart NRPE service.