curl -o /etc/yum.repos.d/CentOS-base.repo https://mirrors.aliyun.com/repo/Centos-7.repo
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
0 0 0 0 0 0 0 0 --:--:-- 0:00:39 --:--:-- 0curl: (6) Could not resolve host: mirrors.aliyun.com; Unknown error
解决办法：
重启网络
systemctl restart network