To backup:
$ sudo -u postgres -i
$ export DB_NAME="mydatabase"
$ pg_dump -Fc "$DB_NAME" > "$DB_NAME"-`date -u +%Y%m%d%H%M%S`.dump
To restore:
$ sudo -u postgres -i
$ export DB_NAME="mydatabase"
$ export DB_DUMP="mydatabase-20140310120842.dump"
$ dropdb "$DB_NAME" || true
$ pg_restore --create "$DB_DUMP" | psql