yum install git
问题：
[root@hcss-ecs-2a6a maven]# yum install git
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
base | 3.6 kB 00:00:00
https://download.docker.com/linux/centos/7/x86_64/stable/repodata/repomd.xml: [Errno 14] curl#7 - "Failed to connect to 2a03:2880:f117:83:face:b00c:0:25de: Network is unreachable"
Trying other mirror.
https://download.docker.com/linux/centos/7/x86_64/stable/repodata/repomd.xml: [Errno 14] curl#7 - "Failed to connect to 2a03:2880:f117:83:face:b00c:0:25de: Network is unreachable"
Trying other mirror.更换镜像源
你可以尝试使用阿里云的 Docker 仓库镜像源。编辑 /etc/yum.repos.d/docker-ce.repo 文件，将内容替换为：
[docker-ce-stable]
name=Docker CE Stable - $basearch
baseurl=https://mirrors.aliyun.com/docker-ce/linux/centos/7/$basearch/stable
enabled=1
gpgcheck=1
gpgkey=https://mirrors.aliyun.com/docker-ce/linux/centos/gpg
然后运行以下命令更新仓库缓存并安装 Docker：
sudo yum makecache fast
sudo yum install docker-ce
通过这些步骤，你应该能够解决网络连接问题并成功安装 Docker。