# mv /etc/yum.repos.d/CentOS-Base.repo
# /etc/yum.repos.d/CentOS-Base.repo.backup
CentOS 5
wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-5.repo
CentOS 6
wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-6.repo
CentOS 7
wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo
# yum makecache
原文：http://www.cnblogs.com/miclesvic/p/6135433.html