Ubuntu 12.10 sem NetworkManager usando rede WPA2

# rfkill 0 unblock
# rfkill 1 unblock
# wpa_passphrase ssid pwd >ssid.conf
# wpa_supplicand -D wext -i wlan0 -c ssid.conf

Se isso funcionar, adicionar a /etc/network/interfaces:

auto wlan0
iface wlan0 inet dhcp
wpa-ssid ssid
wpa-psk pwd