In some countries, it is prohibited to use WiFi without a government permit (certification). If you live in such country, this memo can help you.
You may think it is very easy to disable WiFi interface using the OpenWRT bare control panel LuCi. http://arduino.local/cgi-bin/luci/admin/network/wireless
However, you will be noticed that Yun will reboot every 60 seconds if the WiFi interface is disabled. This behavior is intended by the Yun developer. You have to bypass or "fool" the WiFi detection function in Yun. This requires a small modification to the Yun's Linux part.
Here is an Arduino sketch to make such modification. https://gist.github.com/sgk/6641198 https://gist.github.com/sgk/6641198/raw/c6c36b2c8a9d62036b11335f6515ce3c5ce03ee6/PatchYun.ino
After successfully compiling and running the sketch on Yun, just open a Serial Monitor. You will see messages like "Paching..." and "...Done.". If you see a blue LED to light without flashing, the modification is successful. The sketch does following changes.
- Remove a utility that enables the WiFi hardware.
- Disable to run the WiFi detection daemon which reboots after 60 seconds if WiFi could not be enabled.
- Changed the blue LED meaning to indicate the Linux boot completion by lighting (not flashing).
- Protect the above changes to continue after the factory reset.
I filed an issue for this, and I hope Yun will have this functionality in the next release. https://github.com/arduino/linino/issues/5