Enabling read/write on external drive shared between OS X and Linux (Ubuntu)

Okay, so i’ve had a 1TB external USB for a while which has been formatted for OS X use (HFS+). I’ve been doing a lot of work on Linux (Ubunut 14.04) recently and wanted an easy, fast way to be able to read/write on both operating systems. I dabbled with this briefly a while back but was unsuccessful, but recently I found a little trick to enable read / write on both OS’s! This may seem like basic setup to some, but judging from the amount of forum posts i’ve read on this, it does seem to fox a lot of people…

NOTE: there is a caveat to this; I don’t share this drive with any other computers. If you move a drive between machines then this solution isn’t for you. Read on to find out how to enable this!