steps:

1. mkdir /home/docker（你想要docker存放image的目录）

2. systemctl stop docker

3. vi /usr/lib/systemd/system/docker.service

4. 添加 -g /home/docker

[Unit]

Description=Docker Application Container Engine

Documentation=https://docs.docker.com

After=network.target docker.socket

Requires=docker.socket

[Service]

Type=notify

ExecStart=/usr/bin/docker daemon -g /home/docker -H fd://

MountFlags=slave

LimitNOFILE=1048576

LimitNPROC=1048576

LimitCORE=infinity

[Install]

WantedBy=multi-user.target

5. cp -R /var/lib/docker/* /home/docker/

6. systemctl daemon-reload

7. systemctl start docker

done.