This script allows you to automatically archive and upload a backup of your existing Ghost data to your Dropbox account.
You'll need to follow this tutorial.
Then, you must create an executable script using the code of ghost_backup.sh in this gist (but modifying your blog's path and prefix).
If you have followed the tutorial and both scripts are on the same folder, you should be able to create your first buck by running bash ghost_backup.sh
.
If you want to automatize the backups, you only have to put an entry on the crontab and it will work!