该网址有教程:https://jingyan.baidu.com/article/b7001fe1d1d8380e7382dd72.html
一、下载CentOS7,点击网址下载,地址:http://isoredirect.centos.org/centos/7/isos/x86_64/CentOS-7-x86_64-DVD-1804.iso