file system level backup

i have just switched to posgresql and installed for use with ruby.

i need to move my app and database to a new server. since i can shut
down the server i think it will be easier for me to do a file system
level back up.

when i try to shut the server down i get this message

sudo -u postgres pg_ctl -D /opt/local/var/db/postgresql82/defaultdb
stop
pg_ctl: PID file "/opt/local/var/db/postgresql82/defaultdb/
postmaster.pid" does not exist
Is server running?

it is running.

this is my first time attempting this. can someone suggest an easy
tutorial on this.

also...
i have set up the new server with the same permissions so i should be
able to move the db to the new location.

total newbie