CentOS 7.2 安装图像化界面步骤：
1、安装图像插件 yum groupinstall "GNOME Desktop" "Graphical Administration Tools" -y
2、调整运行级别 ln -sf /lib/systemd/system/runlevel5.target /etc/systemd/system/default.target
3、重启 reboot
参考：
https://cloud.tencent.com/developer/article/1418159?from=information.detail.%E8%85%BE%E8%AE%AF%E4%BA%91centos%E6%9C%8D%E5%8A%A1%E5%99%A8%E5%AE%89%E8%A3%85%E5%9B%BE%E5%BD%A2%E5%8C%96%E7%95%8C%E9%9D%A2