To start/stop/connect/disconnect the syncdaemon, you can use u1sdtool in
a terminal:
u1sdtool -s will start it
u1sdtool -q will stop it
u1sdtool -c will connect it (and start if not running)
u1sdtool -d will disconnect it
The daemon will auto-connect, if you have the local user associated to
an Ubuntu One account, and the token exists in the keyring. If the user
has no token in the keyring, syncdaemon will not connect. If you have
two users logged in locally, and only disconnect one of them from Ubuntu
One, the other will not be affected by that. It is not a system-wide
service, but runs on a per-user basis.
You can also run the ubuntuone-syncdaemon in a terminal with --debug to
get more debug information printed to the console, or set the log
level in ~/.config/ubuntuone/logging.conf to DEBUG.
If you are having a problem, and want to debug it, then it's probably
best to file a bug or support request, and join #ubuntuone IRC on the
freenode network, where we can answer questions in real time and help
you more easily than slowly going back and forth in e-mail. :)