kubespray/roles/network_plugin/calico/templates/systemd-docker.service

[Unit]
Description=Docker Application Container Engine
Documentation=http://docs.docker.com
{% if ansible_os_family == "RedHat" %}
After=network.target
Wants=docker-storage-setup.service
{% elif ansible_os_family == "Debian" %}
After=network.target docker.socket
Requires=docker.socket
{% endif %}

[Service]
Type=notify
{% if ansible_os_family == "RedHat" %}
EnvironmentFile=-/etc/sysconfig/docker
EnvironmentFile=-/etc/sysconfig/docker-network
EnvironmentFile=-/etc/sysconfig/docker-storage
{% elif ansible_os_family == "Debian" %}
EnvironmentFile=-/etc/default/docker
{% endif %}
Environment=GOTRACEBACK=crash
ExecStart=/usr/bin/docker daemon \
          $OPTIONS \
          $DOCKER_STORAGE_OPTIONS \
          $DOCKER_NETWORK_OPTIONS \
          $INSECURE_REGISTRY
LimitNOFILE=1048576
LimitNPROC=1048576
LimitCORE=infinity
MountFlags=slave
TimeoutStartSec=1min

[Install]
WantedBy=multi-user.target