Ubuntu VNC Server - vncserver - vnc4server
Follow
apt-get install gnome-session-fallback
Install and start GDM (I choose GDM instead of lightgdm when it gave me the choice)
apt-get install gdm
if you already installed GDM ,gnome before use
dpkg-reconfigure gdm
Follow
http://www.howtoforge.com/how-to-install-vnc-server-on-ubuntu-14.04
Then edit
~/.vnc/xstartup
with the following: