1. 备份现有源:
mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.bak
2.下载163源
wget http://mirrors.163.com/.help/CentOS7-Base-163.repo mv CentOS7-Base-163.repo CentOS7-Base.repo
3.清理并生成缓存
yum clean all yum makecache
原文：http://www.cnblogs.com/duzishanglu/p/4688034.html