[root@iZuf6fgg72pgf974fd8xs4Z ~]# yum install docker
Docker CE Stable - x86_64                                                                                                                                                                                     14 kB/s | 2.3 kB     00:00    
Errors during downloading metadata for repository 'docker-ce-stable':
  - Status code: 404 for https://mirrors.aliyun.com/docker-ce/linux/centos/3/x86_64/stable/repodata/repomd.xml (IP: 58.215.146.118)
Error: Failed to download metadata for repo 'docker-ce-stable': Cannot download repomd.xml: Cannot download repodata/repomd.xml: All mirrors were tried

解决：

处理方法
进入 /etc/yum.repos.d 目录下，将所有有关 docker 的 repo 全部删掉

cd /etc/yum.repos.d/

rm -rf docker-ce.repo mirrors.aliyun.com_docker-ce_linux_centos_docker-ce.rep.repo