问题解决: 'appstream' 下载元数据失败 : Cannot prepare internal mirrorlist: No URLs in mirrorlist

yum 源的根目录

/etc/yum.repos.d/

修改所有的CentOS文件内容

sed -i 's/mirrorlist/#mirrorlist/g' /etc/yum.repos.d/CentOS-*

sed -i 's|#baseurl=http://mirror.centos.org|baseurl=http://vault.centos.org|g' /etc/yum.repos.d/CentOS-*

更新源为阿里云镜像

wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-8.repo

yum clean all

yum makecache

检测是否可安装

yum grouplist