After a fresh install of Ubuntu 12.04 my WLAN would not connect. I guess I messed around too much trying to get it to work, in any case now wlan0 is not listed anymore when doing iwlist scan.

ifconfig wlan0 up

returns an error

device not found

lspci shows that the computer has a Realtek RTL-8139/8139C/8139C+ Ethernet controller.

3

5 Answers

Is this on a laptop? If so, many laptops have hardware switches that turn of all wireless connectivity. If you can't find it then turn to the manual of your hardware.

On my laptop it is easy to accidentally switch it off.

1

Maybe the wireless killswitch is still locked.

Then you could try to activate wireless with the help of "rfkill - tool for enabling and disabling wireless devices":

sudo /usr/sbin/rfkill unblock wifi

after that you should check if your device appears via ifconfig -a.

Also check the status of the killswitch using

rfkill list

2

Either there was another network card in the output of lspci that you missed, or the wireless card wasn't detected (if it's there, try sudo modprobe <module name>, with the module name from lsmod to get it started (and without the brackets)).

From the model of the ethernet card I take it you've got a laptop, there should be an "RF" sticker on the bottom with a model number on it. Ensure the BIOS doesn't skip tests and disable the splash screen for it, then look for the wireless card when it's booting (hit Pause if it goes too fast to read).

If it doesn't show there, see if it's deactivated in the BIOS; if not, there's probably a hardware problem. If it shows, try booting with another kernel version or OS (a live cd or a bootable memory stick is nice for this) and see if you can detect it again.

5

I have experienced wlan0 missing for a long while. Here is how I fixed it:In BIOS, just to disable the Secure Boot State

For Asus motherboard, clearing secure boot key will automatically disable secure boot state. After that, I did not nothing and I found the wifi connection was available.

You can try unloading and reloading the kernel module for wifi: lsmod | grep wifi Unload the modules you see (rtlwifi, iwlwifi of something else) rmmod If it says module is in use by: Unload that module too , remember it Afterwards, reload the modules modprobe modprobe

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