http://centos.ustc.edu.cn/

cd /etc/yum.repos.d
mv CentOS-Base.repo  CentOS-Base.repo.save
wget http://centos.ustc.edu.cn/CentOS-Base.repo.5
wget http://centos.ustc.edu.cn/epel.repo.5
mv CentOS-Base.repo.5 CentOS-Base.repo
mv epel.repo.5 epel.repo