It uses mysqldump for backups, please do what the manual says and consider using mysqlhotcopy.
Also, don't use this on heavily witten databases as mysqldump will table-lock and you'll have problems. The correct approach is to use mysql replication for this.
Three bash variables you want to edit: USERNAME, PASSWORD, BACKUP_DIR. Own it to root and chmod 0500 or similar.
Configure USERNAME, PASSWORD. Same permissions as with above.