Ubuntu One has a command line tool called u1sdtool. With this, you can start the service
$ u1sdtool --start
To check whether the service is running, check
$ u1sdtool -s State: READY connection: Not User With Network description: ready to connect is_connected: False is_error: False is_online: False queues: WORKING_ON_BOTH
This shows the Ubuntu One sync daemon is ready. Check how to work with Ubuntu One.