To access USB serial port

* In order to pre-mount USB device file system when system boot-up, to add parameter to /etc/fstab (in linux kernel 2.6)

$ vi /etc/fstab

none /proc/bus/usb usbfs defaults,devmode=0666 0 0

* Auto mount it

$ mount -a

ex: you can access USB serial port by device file /dev/ttyUSB0 or ttyUSB1

Reference: http://www.goldfisch.at/knowledge/332