This check is for OpenBSD machines with bioctl(8) supported RAID cards.
The only real caveat with it is that bioctl needs rw permission to /dev/bio. One way to allow for that is by adding an entry to /etc/doas.conf.
This is an example of a setup for NRPE. For checks on the machine running Nagios, use the _nagios user in /etc/doas.conf instead of _nrpe, and of course, no ${SYSCONFDIR}/nrpe.cfg. check_bioctl runs bioctl once for each device, so you will need a doas.conf entry that matches each device you wish to check. If you have multiple RAID volumes, you'll need one permit rules per volume.
/etc/doas.conf:
permit nopass _nrpe as root cmd /sbin/bioctl args ami0 permit nopass _nrpe as root cmd /sbin/bioctl args ami1
${SYSCONFDIR}/nrpe.cfg
:
command[check_bioctl]=${PREFIX}/libexec/nagios/check_bioctl -d ami0 -d ami1
For more information on bioctl(8) see the OpenBSD man page.