New server, copying over some existing NRPE-based checks in Zenoss, but they all error out with “NRPE: Unable to read output” despite all of the commands actually working. /etc/sudoers has the nagios user listed properly, so what’s the problem?
The problem is this line in /etc/sudoers:
Defaults requiretty
Comment that line out, restart nrpe and it works.
Evan Hoffman's Blog 