7 02 2016

To install proprietary NVIDIA driver:

sudo add-apt-repository ppa:xorg-edgers/ppa
sudo apt-get update
sudo apt-get install nvidia-340 nvidia-settings
sudo nvidia-xconfig
sudo reboot

—

To go back to Nouveau driver

#stop lightdm
apt-get –remove purge nvidia*
apt-get install –reinstall xserver-xorg-video-nouveau
apt-get install –reinstall xserver-xorg-core
update-grub
reboot
sudo apt-get install nouveau-firmware
sudo dpkg-reconfigure xserver-xorg

—

Also have a look at possible required or unwanted blacklist entries in /etc/modprobe.d/blacklist* …

Elementary OS “Freya” on Mid-2012 MacBook Pro 15″ – Improving battery life … Elementary OS “Freya”: Using touchegg to add three-finger-swipes between desktop spaces