Raspberry Pi Wifi Adapter

# vi /etc/network/interfaces

auto wlan0
iface wlan0 inet dhcp
    wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf

# ifup wlan0

References :
Edimax EW-7811UN Wifi dongle on Raspbian
Gentoo Forums :: 觀看文章 - [Solved] WPA_Supplicant issues