systemctl cat docker

# /run/systemd/system/docker.service
[Unit]
Requires=torcx.target
After=torcx.target
Description=Docker Application Container Engine
Documentation=http://docs.docker.com
After=containerd.service docker.socket network-online.target
Wants=network-online.target
Requires=containerd.service docker.socket

[Service]
EnvironmentFile=/run/metadata/torcx
Type=notify
EnvironmentFile=-/run/flannel/flannel_docker_opts.env
Environment=DOCKER_SELINUX=--selinux-enabled=true

/run/flannel/flannel_docker_opts.env

vi flannel_docker_opts.env

DOCKER_OPTS="--registry-mirror=https://xxxxx.mirror.aliyuncs.com"

systemctl daemon-reload
systemctl restart docker

ps aux |grep docker

root    831 1.3 0.8 272276 32908 ?    Ssl 16:55  0:00 
/run/torcx/bin/dockerd --host=fd:// --containerd=/var/run/docker/libcontainerd/docker-
containerd.sock --selinux-enabled=true --registry-mirror=https://xxxxx.mirror.aliyuncs.com