Vmware 安装CentOS7后替换yum源
cd /etc/yum.repos.d/
mv CentOS-Base.repo CentOS-Base.repo.bak
wget http://mirrors.163.com/.help/CentOS7-Base-163.repo
mv CentOS7-Base-163.repo CentOS-Base.repo
yum clean all
yum makecache
yum install epel-release检查centos的版本：
[root@shuimo usr]# cat /etc/centos-release
CentOS Linux release 7.4.1708 (Core)