Return code of 255 is out of bounds

Return code of 255 is out of bounds message appears in Nagios console while setting up Linux processes. Below image is for reference where the processes show OK and in green state but still Nagios reports, 255 is out of bounds.

For this issue, the resolution will be to check if nrpe file is properly declared or not with Linux IP. Check if the files are having proper permissions to execute the processes on linux.

1. Check if only_from attribute in /etc/xinetd.d/nrpe contains proper IP to monitor the Linux processes. Please remember that this attribute is separated by spaces and not with a comma.

only_from = 127.0.0.1 <Nagios server ip>

2. Check if there is any network issue between Nagios and Linux machine.

3. check_nrpe command should be working properly irrespective of the error message seen on Nagios UI console. Make sure that check_nrpe returns a proper result first.

4. Check the configuration files and restart the NRPE service once after editing any value so that the changes will get reflected.

Check out my previous entries on Nagios topic here.