1. First, back up the original cent os official source yum
cp /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.bak
2. Get Ali's yum yum source covering local official sources
wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-6.repo
3. Clean yum cache, and generates a new cache
yum clean all
yum makecache