​cd /etc/yum.repos.d​

​[root@dusonglin yum.repos.d]#​

​ mv CentOS-Base.repo   CentOS-Base.repobak     备份repo文件​

​ wget http://mirrors.aliyun.com/repo/Centos-7.repo    从网上下载阿里的repo文件​

​ mv Centos-7.repo CentOS-Base.repo     重命名阿里的repo文件​

​重建缓存​

​yum clean all​

​yum makecache​