I used Digital Ocean's One-Click install for Ghost blog some time ago and then I wanted to update it. It ended up being more work then I'd hoped so hopefully this helps someone.
If you get locked out
# If you get locked out of your droplet: # 1. upload your ~/.ssh/id_rsa.pub file to Dropbox # 2. Then reset Digital Ocean root password # 3. Login through the Digital Ocean web console using new password