I like using Ubuntu One for file synchronization because it offers 5GB of space for free. I ran into a few gotchas where Ubuntu One wouldn’t start synchronizing new files and folders and the output of
u1sdtool --waiting was blank. The solution to this was to tell Ubuntu One to rescan the folder by running these commands at the terminal:
> u1sdtool --list-folders
id=x-x-x-x-x subscribed=True path=/path/to/folder
> u1sdtool --rescan-from-scratch=x-x-x-x-x
After telling Ubuntu One to rescan the folder that isn’t synchronizing, it will start to upload all the files and folders in that folder. This also helps when there are file conflicts or the
u1sdtool --waiting or
u1sdtool --current-transfers is empty and there are files or folders on your computer that haven’t been synchronized.