List USB devices.
- http://askubuntu.com/questions/604158/how-do-i-tell-if-a-usb-thumb-drive-is-usb-3-0
- http://superuser.com/questions/527816/usb-2-0-3-0-how-do-you-tell-the-difference
Hardware examination:
- the port and device are usually blue.
- USB 3 has more pins
Software method:
lsusb
lsusb -D /dev/bus/usb/003/023