CentOS7，切换源

yum 源

备份

mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.backup

下载

wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo

缓存

yum clean all
yum makecache

参考资料

https://blog.csdn.net/qq_37274323/article/details/81107958
https://www.cnblogs.com/shu-sheng/p/12111830.html