sudo mkdir -p /opt/local/var/db/postgresql94/defaultdb
sudo chown postgres:postgres /opt/local/var/db/postgresql94/defaultdb
sudo su postgres -c ‘/opt/local/lib/postgresql94/bin/initdb -D /opt/local/var/db/postgresql94/defaultdb’
/opt/local/lib/postgresql94/bin/postgres -D /opt/local/var/db/postgresql94/defaultdb
or
/opt/local/lib/postgresql94/bin/pg_ctl -D /opt/local/var/db/postgresql94/defaultdb -l logfile start