中國科技大學yum源
cd /etc/yum.repos.d/
mv CentOS-Base.repo CentOS-Base.repo_backup
wget http://centos.ustc.edu.cn/CentOS-Base.repo.5
mv CentOS-Base.repo.5 CentOS-Base.repo
mv CentOS-Base.repo CentOS-Base.repo_backup
wget http://centos.ustc.edu.cn/CentOS-Base.repo.5
mv CentOS-Base.repo.5 CentOS-Base.repo