DUO's bootloader update

1. Unzip the duo_cfe_3_0_usb.zip to USB stick.(There should be /vuplus/duo/cfe_cfe_auto.bin)
2. Insert USB stick into the USB port of duo and power on the box.
3. It takes just a few secs to update.
4. If Duo displays the message "Finished..reboot", remove the USB stick and restart box.
5. To update 6.0 image, you should delete the cfe_cfe_auto.bin at /vuplus/duo in USB stick once bootloader update is finished.