1，登陆root帐号

2，cd /etc/yum.repo.d

3，mv CentOS-Base.repo CentOS-Base.repo.bak
4，wget http://mirrors.aliyun.com/repo/Centos-7.repo
5，mv Centos-7.repo CentOS-Base.repo
6， yum clean all
7， yum makecache
8，yum update

4~5步骤可以wget一步到位的