LXDE - Install LXDE (Lubuntu) for desktop environment Ubuntu 16.04

Install LXDE
The following command will install LXDE. $ sudo apt install -y lubuntu-desktop $ sudo reboot

Uninstall LXDE
The following command will uninstall LXDE. $ sudo apt remove -y lubuntu* lxde* openbox lightdm-gtk-greeter $ sudo apt autoremove -y $ sudo reboot

Prevent Ubuntu Server from auto booting into GUI
You could disable the display manager service with systemctl for example if your display manager is lightdm the run sudo systemctl disable lightdm.service. This will prevent the service from starting at boot.

To start the GUI, Its as simple as starting the service sudo systemctl start lightdm.service

Sources:
 * https://www.hiroom2.com/2017/07/26/ubuntu-1604-lxde-en/
 * https://superuser.com/questions/1106174/boot-ubuntu-16-04-into-command-line-do-not-start-gui