1.进入yum文件夹
cd /etc/yum.repos.d/
2.下载阿里云源
wget "http://mirrors.aliyun.com/repo/Centos-7.repo"
3.备份系统原来的repo文件
mv CentOS-Base.repo CentOS-Base.repo.bak
4.修改Centos-7.repo名称改为CentOS-Base.repo
mv Centos-7.repo CentOS-Base.repo
5.执行yum源的更新命令
yum clean all
yum makecache
yum update
原文：https://www.cnblogs.com/lnsylt/p/14288667.html