Hum... You're right. Seems port jails are broken in 9.2.1.
There is another way
Do
$ cd /usr/ports/sysutils/freeipmi
$ make
Press and validate at all prompts. This will take a little while.
Then install with:
$ make install
Now you can run it. If you have loaded the ipmi kernel module you can use freeipmi as-is, in out of band mode, no need for user/password. If not, check the help on how to set which machine to connect to, the username and password.
To load the ipmi module, the fastest is to exit the jail and type:
$ sudo kldload ipmi
Then go back into The jail and use ipmi-sensors-config to checkout the current configuration, and commit to modify it
OK, I got freeimpi installed and saved the current settings to a file, then changed the Fan1 thru Fan4 Lower Non-Critical Thresholds to 500.000000 and the Lower Critical Thresholds to 400.000000 (had to re-learn vi -- yuk!).
BUT when I tried to commit the changed file I got the response that these values are "out of range." And then I read that these values are not reconfigurable on Supermicro boards anyway, so I still have to put up with the Enermax "T.B Silence" fans either running at full speed all the time or frequently changing over a range from 525rpm to 1575rpm. (But once I have this all figured out, I'll put the FreeNAS box somewhere where it won't be heard anyway.)
BTW, apart from FANA being for the CPU, are each of the other fan connectors intended for fans in specific locations in the case? -- not that I am using a traditional rack-mount server case anyway.