解决 Failed to search for file: cannot update repo ‘appstream’: Cannot prepare internal mirrorlist: No URLs in mirrorlist
因为Centos 8已经停止维护，所以需要改变镜像。
cd /etc/yum.repos.d/
sudo sed -i 's/mirrorlist/#mirrorlist/g' /etc/yum.repos.d/CentOS-*
sudo sed -i 's|#baseurl=http://mirror.centos.org|baseurl=http://vault.centos.org|g' /etc/yum.repos.d/CentOS-*
