gnome centos 7 code example
Example 1: install x centos 7
yum groupinstall "X Window System"
Example 2: install GUI centos 7
# ln -sf /lib/systemd/system/runlevel5.target /etc/systemd/system/default.target
yum groupinstall "X Window System"
# ln -sf /lib/systemd/system/runlevel5.target /etc/systemd/system/default.target