NRPE unable to read output, but why?

You have a rights problem.

Change the command to:

command[check_openmanage]=sudo /usr/lib/nagios/plugins/additional/check_openmanage -s -e -b ctrl_driver=0 bat_charge

(add sudo)

Then, add the nagios-user to the sudoers:

nagios ALL=(ALL) NOPASSWD:/usr/lib/nagios/plugins/additional/check_openmanage

Or you could just chmod the file... That also works.

If you are using CentOS, Red Hat, Scientific or Fedora, make sure to disable Defaults requiretty in the sudoers file.

Short answer : if you're using a Bash plugin, make sure you have a shebang stating which interpreter should be used : #!/bin/bash

I was facing the same issue with a Nagios plugin I wrote myself. The script was running as expected when launched locally, even when running as user nagios using following statement :

$ sudo sudo -s -u nagios
$ /path/to/my/plugin.sh
STATUS: OK

But remote-launching using NRPE from the Nagios3 server was unsuccessful :

$ /usr/lib/nagios/plugins/check_nrpe -H my-nagios-client -c my_plugin
NRPE: Unable to read output

I finally solved this case by adding a shebang in my script, as it appeared that running the script through NRPE did not used the same interpreter as when running through sudo sudo -s -u nagios.