安装过程
首先去网站下载docker安装包，我这里选择和公司服务器上的docker一致的版本：docker-19.03.3.tgz，然后上传到需要安装docker的服务器。
1）首先解压压缩包，此时会在当前目录下生成一个docker目录，在docker目录下全是可执行文件。
tar -xzvf docker-19.03.3.tgz
docker/
docker/docker
docker/runc
docker/ctr
docker/dockerd
docker/docker-init
docker/docker-proxy
docker/containerd-shim-runc-v2
docker/containerd-shim
docker/containerd2）将1）中解压得到的二进制文件全复制到/usr/bin目录下。
cd docker
cp * /usr/bin/3）将docker注册成系统服务
执行“vim /etc/systemd/system/docker.service”命令，然后在文件中添加以下内容，退出并保存。
下面的配置需要注意的是 ： ExecStart=/usr/bin/dockerd，也就是说指明了dockerd所在位置。我第一次安装没有将1）中所有的二进制复制到/usr/bin/，
[Unit]
Description=Docker Application Container Engine
Documentation=https://docs.docker.com
After=network-online.target firewalld.service
Wants=network-online.target
[Service]
Type=notify
ExecStart=/usr/bin/dockerd
ExecReload=/bin/kill -s HUP $MAINPID
LimitNOFILE=infinity
LimitNPROC=infinity
TimeoutStartSec=0
Delegate=yes
KillMode=process
Restart=on-failure
StartLimitBurst=3
StartLimitInterval=60s
[Install]
WantedBy=multi-user.target给文件增加可执行权限
chmod +x /etc/systemd/system/docker.service
systemctl daemon-reload 4）设置开机自启动
systemctl enable docker.service5） 启动docker
systemctl start docker6）测试docker是否启动
docker ps如果打印出如下信息，则表示正确安装，如果提示Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?，则表示docker没有安装正确。
过程中遇到的错误
1）在将docker注册成系统服务时，需要注意的是 ： ExecStart=/usr/bin/dockerd，也就是说指明了dockerd所在位置。我第一次安装没有将1）中所有的二进制复制到/usr/bin/下，造成在执行systemctl start docker时，报错：Process: 28545 ExecStart=/usr/bin/dockerd (code=exited, status=203/EXEC)。这是因为程序没有在/usr/bin下找到dockerd可执行程序，因此报错。
Job for docker.service failed because the control process exited with error code. See "systemctl status docker.service" and "journalctl -xe" for details.
● docker.service - Docker Application Container Engine
Loaded: loaded (/etc/systemd/system/docker.service; disabled; vendor preset: disabled)
Active: failed (Result: start-limit) since 四 2020-11-12 11:27:15 CST; 37s ago
Docs: https://docs.docker.com
Process: 28545 ExecStart=/usr/bin/dockerd (code=exited, status=203/EXEC)
Main PID: 28545 (code=exited, status=203/EXEC)
11月 12 11:27:15 host-90-0-0-80 systemd[1]: Failed to start Docker Application Container Engine.
11月 12 11:27:15 host-90-0-0-80 systemd[1]: Unit docker.service entered failed state.
11月 12 11:27:15 host-90-0-0-80 systemd[1]: docker.service failed.
11月 12 11:27:15 host-90-0-0-80 systemd[1]: docker.service holdoff time over, scheduling restart.
11月 12 11:27:15 host-90-0-0-80 systemd[1]: start request repeated too quickly for docker.service
11月 12 11:27:15 host-90-0-0-80 systemd[1]: Failed to start Docker Application Container Engine.
11月 12 11:27:15 host-90-0-0-80 systemd[1]: Unit docker.service entered failed state.
11月 12 11:27:15 host-90-0-0-80 systemd[1]: docker.service failed.2）关于 /etc/docker/daemon.json 的错误
刚开始遇到1）的错误时，copy了公司其他docker服务器上的 /etc/docker/daemon.json，报错： Process: 3706 ExecStart=/usr/bin/dockerd (code=exited, status=1/FAILURE)。此时主要观察到daemon.json的 “data-root”: “/data/docker”, 然而在安装的时候，我在/data/docker 下放置了解压的二进制文件，导致相关目录无法创建，从而导致docker在读取 /etc/docker/daemon.json后发生错误。
[root@tt init.d]# service docker start
Redirecting to /bin/systemctl start docker.service
Job for docker.service failed because the control process exited with error code. See "systemctl status docker.service" and "journalctl -xe" for details.
# 根据提示使用相关命令查看启动时错误日志
[root@tt init.d]# systemctl status docker.service
docker.service - Docker Application Container Engine
Loaded: loaded (/usr/lib/systemd/system/docker.service; enabled; vendor preset: disabled)
Active: failed (Result: start-limit) since Mon 2018-07-02 22:20:05 EDT; 10s ago
Docs: https://docs.docker.com
Process: 3706 ExecStart=/usr/bin/dockerd (code=exited, status=1/FAILURE)
Main PID: 3706 (code=exited, status=1/FAILURE)
Jul 02 22:20:05 localhost systemd[1]: docker.service: main process exited, code=exited, status=1/FAILURE
Jul 02 22:20:05 localhost systemd[1]: Failed to start Docker Application Container Engine.
Jul 02 22:20:05 localhost systemd[1]: Unit docker.service entered failed state.
Jul 02 22:20:05 localhost systemd[1]: docker.service failed.
Jul 02 22:20:05 localhost systemd[1]: docker.service holdoff time over, scheduling restart.
Jul 02 22:20:05 localhost systemd[1]: start request repeated too quickly for docker.service
Jul 02 22:20:05 localhost systemd[1]: Failed to start Docker Application Container Engine.
Jul 02 22:20:05 localhost systemd[1]: Unit docker.service entered failed state.
Jul 02 22:20:05 localhost systemd[1]: docker.service failed.