1.安装Wget

yum -y install wget

2.备份本地yum源

mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo_bak

3.获取阿里yum源配置文件

wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo

4.更新yum缓存

yum makecache

然后就可以了