[root@betty ~]# cd /etc/yum.repos.d/
[root@betty yum.repos.d]# wget http://mirrors.163.com/.help/CentOS7-Base-163.repo
[root@betty yum.repos.d]# yum makecache
[root@betty yum.repos.d]# yum -y update
···
Loading mirror speeds from cached hostfile
* base: mirrors.163.com
* extras: mirrors.163.com
* updates: mirrors.163.com
···