If you receive the error above in Nagios, the workaround is to exclude tracefs from the check_disk command.
Login to your client server,
nano /etc/nagios/nrpe.cfg
find the check_disk and add –exclude-type=tracefs
It will looks like this:
/usr/lib/nagios/plugins/check_disk -e --exclude-type=tracefs
/etc/init.d/nagios-nrpe-server restart