DC 5V adapter polarity


My queuestion is about the DC 5V power jack of beagle bone black.
Is the outer part of the power jack is ground or 5V?
DC 5V power adpater which I would purchase has an option for the polarity.

Thanks in advance

J.Hwan Kim

Center positive, as described in the System Reference Manual and a shown in the schematic. Outside ring is ground.