centos8运行更新时提示Error: Failed to download metadata for repo ‘appstream’: Cannot prepare internal mirrorlist: No URLs in mirrorlist

解决方法：

sed -i 's/mirrorlist/#mirrorlist/g' /etc/yum.repos.d/CentOS-Linux-*
sed -i 's|#baseurl=http://mirror.centos.org|baseurl=http://vault.centos.org|g' /etc/yum.repos.d/CentOS-Linux-*
sudo dnf install centos-release-stream -y
sudo dnf swap centos-{linux,stream}-repos -y
sudo dnf distro-sync -y

原文地址：https://flutterq.com/failed-to-download-metadata-for-repo-appstream-cannot-prepare-internal-mirrorlist-no-urls-in-mirrorlist