check this post out:
Applies also to your case (you have OH2Beta5 Online installed). To go to the new snapshots from the unstable repo (or to RC1 from the testing repo) you need to perform: sudo apt-get install openhab2 over the existing, older openhab2-online package version. [Link]
It will upgrade your system without losing any settings/configs (a backup is always a good move in advance of course)