Wifi adapter detected but doesn't work

Question

I started my Raspberry Pi 2, connected to an external monitor. Everything works as supposed.

I connected my USB Wifi adapter and it's being detected by the pi:

$ lsusb
...
Bus 001 Device 04: ID 0bda:818b Realtek Semiconductor Corp.
...

However, there are no wifi networks:

$ iwconfig
lo        no wireless extensions

eth0      no wireless extensions

Realizing I don't have Internet connection on the raspberry, how can I make the wifi connection work?

I'm running Raspbian. So, how can I make it work (maybe some missing packages?)?

---

Relevant output:

$ cat /etc/network/interfaces
auto lo
iface lo inet loopback

auto eth0
allow-hotplug eth0
iface eth0 inet manual

auto wlan0
allow-hotplug wlan0
iface wlan0 inet manual
wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf

auto wlan1
allow-hotplug wlan1
iface wlan1 inet manual
wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf


auto wlan0
allow hotplug wlan0
iface wlan0 inet dhcp
        wpa-ssid "..."
        wpa-psk "..."
$ uname -r
3.18.13-v7+
$ ls /lib/modules/3.18.13-v7+/kernel/drivers/net/wireless/
at76c50x-usb.ko  brcm80211    mac80211_hwsim.ko  rt2x00     zd1211rw
ath              hostap       mwifiex            rtl818x
b43              libertas     p54                rtl8192cu
b43legacy        libertas_tf  rndis_wlan.ko      zd1201.ko
pi@raspberrypi:~$ cat /etc/network/interfaces
auto lo
iface lo inet loopback

auto eth0
allow-hotplug eth0
iface eth0 inet manual

auto wlan0
allow-hotplug wlan0
# wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf
iface wlan0 inet dhcp
        wpa-ssid "Edimax"
        wpa-psk "<password>"


auto wlan1
allow-hotplug wlan1
iface wlan1 inet manual
wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf

Answer 1

Ther reason why you don't have a wlan0 is that you don't have a wlan0 stanza in your /etc/network/interfaces. Go there and make a setting for wlan0 by typing sudo nano /etc/network/interfaces and add the example stanza

auto wlan0
allow hotplug wlan0
iface wlan0 inet dhcp
        wpa-ssid "ssidofyourrouter"
        wpa-psk "passwordofyourrouter"

If you have auto line, allow line is not compulsory, for more information check https://wiki.debian.org/WiFi/HowToUse

iface wlan0 inet dhcp isn't your only option, you can set it manual or static too but the settings will be different. After you added the stanza I've put above to /etc/network/interfacestype sudo ifdown wlan0 and then sudo ifup wlan0.

If you have entered the right settings you will be connected to the router you have been specified in the stanza by "ssidofyourrouter" and "passwordofyourrouter". By dhcp(dynamic host configuration protocol) then your Pi will be assigned an IP between the specified interval in your router settings.

Answer 2

The NOOBS kernel does not have a driver for this USB device. Try using the Raspbian image instead.

Ref: https://github.com/pvaret/rtl8192cu-fixes/issues/50#issuecomment-129484228