CentOS Linux 8作為RHEL 8的復刻版本，生命周期縮短，於2021年12月31日停止更新並停止維護（EOL）
yum 更新提示 Error: Failed to download metadata for repo 'AppStream'
Repository epel is listed more than once in the configuration CentOS-8 - AppStream 8.3 kB/s | 2.3 kB 00:00 Errors during downloading metadata for repository 'AppStream': - Status code: 404 for http://mirrors.cloud.aliyuncs.com/centos/8/AppStream/x86_64/os/repodata/repomd.xml (IP: 100.100.2.148) Error: Failed to download metadata for repo 'AppStream': Cannot download repomd.xml: Cannot download repodata/repomd.xml: All mirrors were tried
解決辦法參考：https://blog.csdn.net/qq_47431361/article/details/122802111