If you are a true CLI user you can skip this article. But if you want a little more comfort and speed working with applications after installing Ubuntu server OS (which comes without graphical interface by the way) you may install GUI interface in only one step. Just type the following:
sudo apt-get install ubuntu-desktop
After installation reboot the system for changes to take effect.
If you would like to have the ability to login as root user aftewards, see article Enabling ROOT Account in Ubuntu.By privilege15