CentOS7更新阿里云yum源，​​参考阿里云官方文档​​，操作如下：

1，备份旧源文件

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

2，下载新源文件

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

或者

curl -o /etc/yum.repos.d/CentOS-Base.repo https://mirrors.aliyun.com/repo/Centos-7.repo

3，清理旧缓存

yum clean all

4，生成新缓存

yum makecache