Please refer to Axel and Luis
messages. Did you install the Vanilla version or the Opensuse one? I
guess you used the OpenSuse installation then proceed as per Axel's
instructions.
or you may use the postgres user to check the database owner:
sudo su postgres
psql -l (to have a list of all databases and their owners)
Once you have the owner, you should switch back to it and proceed by using that username