I've uploaded some files to Ubuntu One from my home laptop and begin to download it on my work laptop. Then I've got a USB and copied these files directly through the USB driver. My problem now is that Ubuntu One still downloading these files although I've copied them to Ubuntu One folder. I need it to consider the already existing files as synced and don't download it again. And I need Ubuntu One for further use so I can't simply quit it. How could I mark the already existing files as synced ?
Ubuntu One maintains a database of files it has synced. If you copy files from your Ubuntu One folder of one computer to another using the USB drive, the Ubuntu One data base is not updated. So it will sync those files again.
I don't know any way of manually messing with Ubuntu One's internal database. It may be best not to copy files across computers that are to be synced by Ubuntu One.