Lenovo Thinkpad X240 comes with RealTek RTL8192EE chipset. Surprisingly the driver does not come built into Ubuntu 14.04 and earlier versions. However this device is supported on Ubuntu 14.10 (Utopic Unicorn)
If you are using earlier version of Ubuntu or Linux Mint 17, the following instructions may help you
The bug is reported on Launchpad and some workarounds have been suggested:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1239578
One solution (see #38) is to download the OEM driver from the following link:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1239578/+attachment/4057550/+files/rtl_92ce_92se_92de_8723ae_88ee_8723be_92ee_linux_mac80211_0017.1016v2.2013.tar.gz
You can also download it from here:
http://netbook-remix.archive.canonical.com/updates/pool/public/o/oem-wireless-rtl-92ce-92se-92de-8723ae-88ee-8723be-92ee-dkms/
or from here (local link)
https://drive.google.com/file/d/0B1WmoEhM2mFOeEo5X2RCdm9RZVU/view?usp=sharing
unzip it .... compile it ... and insert it ... "make" should work ...
Insert the module by using the following command:
$ sudo modprobe rtl8192ee
$ lsmod | grep rtl8192
Probably you need to reboot. Just try some of the following commands to configure your wifi:
$ sudo iwconfig
$ sudo lshw -C Network
$ sudo iwlist wlan0 scan
$ nm-tool
One problem that people have reported about this driver is that it drops connection every now and then. You need to reboot just to get it working again. This is really annoying. A workaround that works for me is to run the following command:
$ sudo killall NetworkManager
this kills and then restarts the network manager and it connects to the wifi again.