备份原来的
mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.backup
阿里yum源
wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo
生成缓存
yum clean all
yum makecache
参考文章：博客园Tsugar
原文：https://www.cnblogs.com/sillage/p/13891275.html