pg_hba.conf

local   all             postgres                                peer

# TYPE  DATABASE        USER            ADDRESS                 METHOD

# "local" is for Unix domain socket connections only
local   all             all                                     peer
# IPv4 local connections:
host    all             all             127.0.0.1/32            md5
# IPv6 local connections:
host    all             all             ::1/128                 md5

local   xnat            xnat01          localhost               trust


also 1234 worked when asked for password here:
$ sudo -i -u postgres
postgres@klein:~$ psql -h localhost  -t -P format=unaligned -c 'show hba_file';
Password:
/etc/postgresql/9.4/main/pg_hba.conf
postgres@klein:~$ vi /etc/postgresql/9.4/main/pg_hba.conf