Taken from [[http://www.cyberz.org/blog/2009/01/03/nagios-nrpe-and-sudo-nrpe-unable-to-read-output/]]

Nagios nrpe and sudo: “NRPE: Unable to read output”
Filed under: Unix — Tags: Linux, Nagios, Sudo, Unix — andrea @ 7:21 pm

On CentOS 5 (and RedHat EL as well), you can encounter the following behaviour when configuring an nrpe plugin with sudo:

  [andrea@feyd ~]$ /usr/lib/nagios/plugins/check_nrpe -H 1.2.3.4 -c check_md_raid
  NRPE: Unable to read output


Given that check_md_raid is defined as follows, in nrpe.conf:

  command[check_md_raid]=sudo /usr/local/bin/nagios_check_md_raid

And given its relative /etc/sudoers line for completeness as follows:

  nagios ALL=(ALL) NOPASSWD:/usr/local/bin/nagios_check_md_raid

Then the problem is in the requiretty options in /etc/sudoers, enabled by default on CentOS. Simply comment it as follows:

  #Defaults requiretty

After that the plugin should work as expected:

  [andrea@feyd ~]$ /usr/lib/nagios/plugins/check_nrpe -H 1.2.3.4 -c check_md_raid
  RAID OK: All arrays OK [1 array checked]