1.安裝wget
yum install -y wget
2.完事前都做備份
mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.backup
3.下載下傳阿裡雲鏡像檔案
wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo
4.清理緩存
yum clean all
5.生成緩存
yum makecache
6.更新最新源設定
yum update -y