~# yum update
Docker CE Stable - x86_64 0.0 B/s | 0 B 02:00
Errors during downloading metadata for repository 'docker-ce-stable':
- Curl error (28): Timeout was reached for https://download.docker.com/linux/centos/8/x86_64/stable/repodata/repomd.xml [Connection timed out after 30000 milliseconds]
Error: Failed to download metadata for repo 'docker-ce-stable': Cannot download repomd.xml: Cannot download repodata/repomd.xml: All mirrors were tried这可能是由于YUM配置文件中包含了Docker仓库的配置，或者您的yum源中包含了Docker的相关依赖。您可以尝试以下步骤解决问题：
1. 查看YUM配置： 查看 `/etc/yum.repos.d/` 目录下是否有与Docker相关的repo文件，如`docker.repo`或`docker-ce.repo`，并临时移除或注释掉相关配置。
本人通过查看`/etc/yum.repos.d/` 目录，发现有docker-ce.repo，打开
[docker-ce-stable]
name=Docker CE Stable - $basearch
baseurl=https://downl
