Dmitry Litvintsev <litvinse@fnal.gov> writes:
> Apparently default user is extracted from kerberos ticket. Is it possible
> to disable this behavior and take current unix user as default user.
We no longer do that as of 8.4 and later. You could possibly back-patch
the change if you are not in a position to update to 8.4:
http://archives.postgresql.org/pgsql-committers/2009-01/msg00163.php
regards, tom lane