I’m going to walk you through the process of setting this up with that particular app and connecting the app to vsftp, running on Ubuntu Server 16.10. There’s actually a really simple solution out there that can be cobbled together, which involves an FTP server and the FolderSync app. If you want them to sync with a particular cloud service, that is always possible but what if you want to back them up to a local machine? You might have particular set of files and folders that are proprietary and should only be backed up within your local network. However, there could be local folders that are not backed up. Your Android device is automatically backed up to the cloud–at least much of it is. Looking for a creative solution for a local cloud storage for Android? Jack Wallen shows you how with the help of an FTP server and FolderSync.
How to set up an easy local backup for Android device folders