详细步骤：
1、下载docker
下载地址:https://download.docker.com/linux/static/stable/x86_64/
本篇以docker-18.06.3-ce.tgz为例
2、上传至服务器指定路径后解压安装文件
tar -zxvf docker-18.06.3-ce.tgz
3、将解压后的文件夹复制到指定目录（随意）
cp ./docker/* /usr/bin
4、创建docker.service文件
cd /etc/systemd/system/
touch docker.service
5、编辑docker.service文件
把下面的内容复制进去即可
[Unit]
Description=Docker Application Container Engine
Documentation=https://docs.docker.com
After=network-online.target firewalld.service
Wants=network-online.target
[Service]
Type=notify
# the default is not to use systemd for cgroups because the delegate issues still
# exists and systemd currently does not support the cgroup feature set required
# for containers run by docker
ExecStart=/usr/bin/dockerd --selinux-enabled=false --insecure-registry=192.168.212.15
ExecReload=/bin/kill -s HUP $MAINPID
# Having non-zero Limit*s causes performance problems due to accounting overhead
# in the kernel. We recommend using cgroups to do container-local accounting.
LimitNOFILE=infinity
LimitNPROC=infinity
LimitCORE=infinity
# Uncomment TasksMax if your systemd version supports it.
# Only systemd 226 and above support this version.
#TasksMax=infinity
TimeoutStartSec=0
# set delegate yes so that systemd does not reset the cgroups of docker containers
Delegate=yes
# kill only the docker process, not all processes in the cgroup
KillMode=process
# restart the docker process if it exits prematurely
Restart=on-failure
StartLimitBurst=3
StartLimitInterval=60s
[Install]
WantedBy=multi-user.target
切记检查复制过去后文本的完整性，很多情况下头部会丢失几个字符，导致失败！
6、添加可执行权限
chmod +x docker.service
7、加载docker.service
systemctl daemon-reload
8、启动docker
systemctl start docker
9、查看docker
systemctl status docker
10、设置开机自启
systemctl enable docker.service
恭喜你已经安装好了！