1，进入yum源配置目录
cd /etc/yum.repos.d
2，备份已有的源地址
mv CentOS-Base.repo CentOS-Base.repo.backup
3、更换源地址
wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo
4，执行yum命令，立即生效，生成缓存
yum makecache
原文：https://www.cnblogs.com/llody/p/11428682.html