1.首先备份原来的cent os官方yum源
cp /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.bak
2.获取阿里的yum源覆盖本地官方yum源
wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-6.repo
3.清理yum缓存，并生成新的缓存
yum clean all yum makecache