1. #/bin/bash
    2. yum install wget -y
    3. cd /etc/yum.repos.d/   
    4. mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.backup
    5. wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo
    6. enabled=0
    7. yum clean all
    8. yum makecache