root@hostname:/home/pi# ifup wlan0
wlan0: ERROR while getting interface flags: No such device
Error for wireless request "Set Encode" (8B2A) :
    SET failed on device wlan0 ; No such device.
Error for wireless request "Set ESSID" (8B1A) :
    SET failed on device wlan0 ; No such device.
Cannot find device "wlan0"
Failed to bring up wlan0.