ossimUpdate

In order to add a (GNOME) desktop to CentOS 7 issue the following commands in your (elevated) terminal:

  1. yum groupinstall "GNOME Desktop" 
  2. unlink /etc/systemd/system/default.target
  3. ln -sf /lib/systemd/system/graphical.target /etc/systemd/system/default.target
  4. reboot the system

After the reboot you should now face a working GUI environment...