I have updated my CentOS desktop and tried to restart(shutdown -r now). But I lost the GUI. I tried ctrl+alt+Fn and also#yum -y groups install GNOME Desktop#startx#yum install lightdm#yum group install X Windows systemBut still facing the same problem (only command line interface is working).  Please suggest me a solution.No changes even after rebooting. Please suggest me a way (WITHOUT LOSS OF DATA). Or can I somehow go back to my previous version?
CentOS 6.9 GUI Problem
centos;gui;desktop;gnu