Thank you for your advice. Do I get you right: if I remove and reinstall the "openmediavault" package via apt on the commandline, the configuration of my system should remain untouched?
If something goes wrong: which files from a backup would I use to restore the configuration?
And YES! OMV on a RasPi2 is what I want!
Perfect for hosting few files that from time to time have to be accessed via internet. No need for more speed and more money to spend.