CoreOS cloud-config with docker tcp socket

gistfile1.txt

#cloud-config
      coreos:
        etcd:
<% if @host.params['etcd_discovery_url'] -%>
          discovery: <%= @host.params['etcd_discovery_url'] %>
<% end -%>
          addr: <%= @host.ip %>:4001
          peer-addr: <%= @host.ip %>:7001
        units:
          - name: etcd.service
            command: start
          - name: fleet.service
            command: start
          - name: docker-tcp.socket
            command: start
            enable: yes
            content: |
              [Unit]
              Description=Docker Socket for the API
              
              [Socket]
              ListenStream=2375
              BindIPv6Only=both
              Service=docker.service
              
              [Install]
              WantedBy=sockets.target
              
          - name: enable-docker-tcp.service
            command: start
            content: |
              [Unit]
              Description=Enable the Docker Socket for the API
              
              [Service]
              Type=oneshot
              ExecStart=/usr/bin/systemctl enable docker-tcp.socket
      
      ssh_authorized_keys:
<% if @host.params['ssh_authorized_keys'] -%>
        - "<%= @host.params['ssh_authorized_keys'] %>"
<% end -%>