From the mind of a G33k
How To Add Bulk users in FreeNAS 11.2 via API
To use this script, create a csv file with the following 3 fields.
Name this file "new_users.csv" and put it in the same directory as "lgfnblkadd.py"
You will need to create your groups via the FreeNAS portal before continuing
You will need to obtain your Group ID's by logging into your FreeNAS appliance then going to the following URL: http://xx.xx.xx.xx/api/v1.0/account/groups/ (where xx.xx.xx.xx is your appliance IP). The highlighted line is the group ID you will need to include in your csv file.