[SOLVED] Ecobee binding losing authorization on restart

I have been running the ecobee binding for a few months with OH2 and raspberryPi. Works great except annoyingly after every restart it loses authentication and I have to redo the pin on ecobee.com. I have read on the wiki to delete the .java directories, but it is not clear to me where they are (or should be) exactly and I could not locate them using the find command.
One other conspicuous message I see at the beginning of OH2 restart is below, which might be related.
I installed OH2 using apt-get and I am wondering if there is some sort of user permission problem. I know just enough about Linux to be dangerous so any help would be appreciated.

15:32:57.467 [WARN ] [java.util.prefs                     ] - java.io.IOException: Permission denied
15:29:27.581 [WARN ] [org.openhab.io.net.http.HttpUtil    ] - Method failed: HTTP/1.1 401 Unauthorized
15:29:27.585 [ERROR] [inding.ecobee.internal.EcobeeBinding] - Error retrieving tokens: authorization_pending
15:29:27.586 [WARN ] [inding.ecobee.internal.EcobeeBinding] - Periodic poll skipped for 'DEFAULT_USER'.

@watou: would you offer a guess before I try reinstalling?

The server should be running under the openhab user, so the directory ~openhab/. java/.userPrefs should be where the tokens are stored. Make sure the permissions and rw file system are suitable for that directory.

Thanks for the hint John.

For some reason ~openhab was not set. I have a 2nd rPi system that is working and so I was able to see ~openhab is set to /var/lib/openhab2, which contains a .java directory. Checking this directory on the forgetful system did not show .java. After stopping OH2, setting ~openhab correctly: sudo usermod -d /var/lib/openhab2 openhab, restarting OH2 and activating another pin, .java appeared!

Thank you for your time and effort on a great binding.