参考：https://developer.aliyun.com/mirror/centos?spm=a2c6h.13651102.0.0.3e221b11jDTRbY
1.yum -y install wget
2.备份
mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.backup
3.下载新的 CentOS-Base.repo 到 /etc/yum.repos.d/
wget -O /etc/yum.repos.d/CentOS-Base.repo https://mirrors.aliyun.com/repo/Centos-7.repo