sudo -s

cp /etc/network/interfaces /etc/network/interfaces.orig

nano /etc/network/interfaces

auto lo
iface lo inet loopback
iface eth0 inet dhcp
auto wlan0
allow-hotplug wlan0
iface wlan0 inet dhcp
wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf

nano /etc/wpa_supplicant/wpa_supplicant.conf

ctrl_interface=DIR=/var/run/wpa_supplica­nt GROUP=netdev
update_config=1

network={
ssid="MEINE-SSID"
scan_ssid=1
proto=RSN
key_mgmt=WPA-PSK
pairwise=CCMP
group=TKIP
psk="MeinPasswort"
}