A colleague of mine was having issues getting the wifi working on his Ubuntu laptop. The interface would show up but it would never pick up any network. Since Windows XP was failing to install on this machine there was no way to check if the wireless adapter was broken. Because I was working in the dark, without doc I thought I would keep a note online to avoid someone else to spend a couple hours on that.
This was the only clue that something was weird, a "radio off" in iwconfig:
# iwconfig eth2 radio off ESSID:off/any Mode:Managed Channel:0 Access Point: Not-Associated Bit Rate=0 kb/s Tx-Power=off Sensitivity=8/0</pre>
The man page for iwconfig(8) had one mention of "radio" for the txpower parameter. After a few tries with this parameter, nothing improved.
The problem is that this laptop comes with BOTH a software and a hardware wifi kill switch. One quick way to pass the software kill switch is to:
# echo 0 > /sys/bus/pci/devices/*/rf_kill
Note that you need a fairly recent version of the IPW2200 driver. Also note that most distributions will do that for you anyways. If you still get a "radio off" you still have to bypass the hardware kill switch by keeping the transparent led/button in front of your laptop pressed for a couple seconds.
Last updated: 2009-11-15