Version 2.5 now shows a status in the web page if the USB sync service is running (and synchronising your media from the pen drive). 

the message disappears once the sync has completed.

The USB sync service will mount the pen drive on plugging in to the Raspberry pi, check the pen drive file system is not damaged (repair if possible) then use rsync to copy any new media over to /var/lid/minidlna folder then unmount the pen drive and then restart the minidlna service (which then scans the media directory again).

this has been a really difficult task to get working but got there in the end. permissions, permissions, permissions..... and executable's. grr

picture during synchronisation