1、下载repo文件 

wget http://mirrors.163.com/.help/CentOS7-Base-163.repo

2、备份并替换系统的repo文件 

cp CentOS7-Base-163.repo /etc/yum.repos.d/ 

cd /etc/yum.repos.d/ 

mv CentOS-Base.repo CentOS-Base.repo.bak 

mv CentOS7-Base-163.repo CentOS-Base.repo

3、执行yum源更新命令 

yum clean all 

yum makecache 

yum update