unknown interface wlan0

[Ralf Mardorf]

Hi,

for my Ubuntu Quantal with Linux 3.5.0-18-lowlatency x86_64 the LED of my USB 
WiFi automatically starts to flash during startup, but it doesn't come up 
for my Kubuntu Saucy with Linux 3.11.0-19-lowlatency x86_64.


This is equal for Quantal and Saucy:


root at saucy:~# lsusb | grep WLAN
[snip] Realtek Semiconductor Corp. RTL8191SU 802.11n WLAN Adapter

root at saucy:~# lsmod | grep r8
r8712u                184158  0 
r8169                  67581  0 
[snip]


Infos about my Saucy install:


root at saucy:~# iwlist scan
ppp0      Interface doesn't support scanning.

eth0      Interface doesn't support scanning.

lo        Interface doesn't support scanning.

wlan0     Interface doesn't support scanning : Network is down

root at saucy:~# ifup wlan0
Ignoring unknown interface wlan0=wlan0.


Quantal's /etc/network/interfaces:


root at saucy:~# cat /media/rocketmouse/q/etc/network/interfaces 
# interfaces(5) file used by ifup(8) and ifdown(8)
auto lo
iface lo inet loopback


Saucy's /etc/network/interfaces:

root at saucy:~# cat /etc/network/interfaces 
# interfaces(5) file used by ifup(8) and ifdown(8)
auto lo
iface lo inet loopback

auto dsl-provider
iface dsl-provider inet ppp
pre-up /sbin/ifconfig eth0 up # line maintained by pppoeconf
provider dsl-provider

auto eth0
iface eth0 inet manual