centos7-更换国内镜像源

1.安装wget
yum install -y wget

2.备份服务器原有的yum源文件
mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.backup

3.下载阿里云镜像文件
wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo

4.清理缓存、生成缓存
yum clean all
yum makecache