~ : sudo mkdir -p /opt/local/var/db/postgresql83/defaultdb
Password:
 ~ : sudo chown postgres:postgres /opt/local/var/db/postgresql83/defaultdb
 ~ : sudo su postgres -c '/opt/local/lib/postgresql83/bin/initdb -D /opt/local/var/db/postgresql83/defaultdb'
The files belonging to this database system will be owned by user "postgres".
This user must also own the server process.

The database cluster will be initialized with locale en_US.UTF-8.
The default database encoding has accordingly been set to UTF8.
The default text search configuration will be set to "english".

fixing permissions on existing directory /opt/local/var/db/postgresql83/defaultdb ... ok
creating subdirectories ... ok
selecting default max_connections ... 20
selecting default shared_buffers/max_fsm_pages ... 2400kB/20000
creating configuration files ... ok
creating template1 database in /opt/local/var/db/postgresql83/defaultdb/base/1 ... ok
initializing pg_authid ... ok
initializing dependencies ... ok
creating system views ... ok
loading system objects' descriptions ... ok
creating conversions ... ok
creating dictionaries ... ok
setting privileges on built-in objects ... ok
creating information schema ... ok
vacuuming database template1 ... ok
copying template1 to template0 ... ok
copying template1 to postgres ... ok

WARNING: enabling "trust" authentication for local connections
You can change this by editing pg_hba.conf or using the -A option the
next time you run initdb.

Success. You can now start the database server using:

    /opt/local/lib/postgresql83/bin/postgres -D /opt/local/var/db/postgresql83/defaultdb
or
    /opt/local/lib/postgresql83/bin/pg_ctl -D /opt/local/var/db/postgresql83/defaultdb -l logfile start