I wrote this tool to set the fan speed on my NAS, based on the ASRock C2750D4I motherboard.
The information about the ipmitool format came from this forum post:
https://lime-technology.com/forum/index.php?topic=39238.msg372263#msg372263
I used perl as I wanted the script to run with no dependencies on FreeNAS.
Simple usage:
fanctrl set FRNT_FAN1=100 FRNT_FAN2=100
Improvements welcome