This is just a quick post, mainly so I have a reference to remind myself next time I need to do this. Auto mounting internal hard drives seems way too complicated in Ubuntu - In my opinion, they should be automatically mounted by the OS by default as I can't think of a use-case where a user wouldn't want an internal drive mounted all the time. Any way, to auto mount a drive, first create a folder to act as the mount point. I chose 'Morty' as the name of the drive and created the folder in /media/
sudo mkdir /media/garry/Morty
You then need to grant the correct permissions to this folder:
sudo chown garry:garry /media/garry/Morty
Get the unique ID of the drive (it's UUID) using this command:
/etc/fstab by appending a new line at the bottom of the file, similar to that below (obviously the Morty drive is formatted as ext4):
sudo nano /etc/fstab UUID=<enter the UUID without brackets> /media/garry/Morty ext4 defaults 0 2
Reboot and you're done.