【From】 https://www.cnblogs.com/lpbottle/p/7875400.html
1. 备份原来的yum源
mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.backup
2. 下载阿里云的CentOS-Base.repo 到/etc/yum.repos.d/
curl -o /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo
3. 清理缓存
sudo yum clean all
4. 生成新的缓存
sudo yum makecache
原文:https://www.cnblogs.com/pekkle/p/10544017.html