1. backup /etc/yum.repos.d/CentOS-Base.repo 
    cp /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.bak
  2. install aliyun CentOS-Base.repo 
    wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo
yum clean all
yum makecache
  3. install EPEL (Extra Packages for Enterprise Linux) repo 
    yum -y install epel-release
yum clean all
yum makecache
  4. install ELRepo (hardware related packages)