The Tonido backup application does not support backing up inside your plug. Following describes how to create a backup from usbdisk A to usbdisk B, both connected to your plug.

First you need to install rsync via apt-get install rsync. Then you can give this command (change for your setup):

rsync -av --delete --exclude xxx/ --backup --backup-dir=yyy/`date +%Y-%m-%d` /zzz1 /zzz2 >> /vvvv/rsync.log 2>&1


* --delete means it removes items from the backup which are no longer on the original
* --exclude xxx means it excludes folder xxx from the backup
* -- in the backup dir yyy it keeps a copy of items deleted from the backup in a folder with the date (extra safety)
* /zzz1 is the original folder and /zzz2 is location of backup
* in /vvv a log file is created

You can also create a cronjob for this command, so it runs automatically at a specified interval. Easiest way to do this is via webmin.