centos8 更换阿里云源

1、备份原文件
mv /etc/yum.repos.d/CentOS-Base.repo /etc/yum.repos.d/CentOS-Base.repo.backup
2、去阿里镜像站下载，具体链接和文件名看实际情况

wget -O /etc/yum.repos.d/CentOS-Base.repo https://mirrors.aliyun.com/repo/Centos-vault-8.5.2111.repo

3、生成新缓存
yum makecache