Docker: override the systemd unit to enable the http socket needed by the external clients.

library/roles/docker/defaults/main.yml

@@ -30,5 +30,6 @@ docker_user_home: /home/docker
 docker_defaults_file: /etc/default/docker
 docker_enable_tcp_socket: False
 docker_tcp_socket_port: 2375
+docker_api_port: 2376
 docker_tcp_socket_host: 127.0.0.1
 

library/roles/docker/tasks/pkgs.yml

@@ -19,8 +19,27 @@
 
     - name: Install the Docker default options
       template: src=docker-default.j2 dest={{ docker_defaults_file }} owner=root group=root mode=0644
+      when: ansible_service_mgr != 'systemd'
       notify: Restart docker
 
+    - name: Create the docker service systemd directory
+      file: dest=/etc/systemd/system/docker.service.d state=directory mode=0755
+      when: ansible_service_mgr == 'systemd'
+      tags: [ 'docker', 'docker_systemd' ]
+
+    - name: Install the Docker additional systemd unit
+      template: src=docker-systemd-override.conf.j2 dest=/etc/systemd/system/docker.service.d/override.conf owner=root group=root mode=0644
+      when: ansible_service_mgr == 'systemd'
+      notify: Restart docker
+      register: reload_systemd
+      tags: [ 'docker', 'docker_systemd' ]
+
+    - name: systemd reload
+      command: systemctl daemon-reload
+      when: reload_systemd is defined and reload_systemd is changed
+      tags: [ 'docker', 'docker_systemd' ]
+
+
     - name: Ensure that the service is started and enabled
       service: name=docker state=started enabled=yes
 

library/roles/docker/templates/docker-systemd-override.conf.j2

@@ -0,0 +1,7 @@
+[Service]
+ExecStart=
+{% if docker_swarm %}
+ExecStart=/usr/bin/dockerd -H tcp://0.0.0.0:{{ docker_api_port }} -H fd:// --containerd=/run/containerd/containerd.sock
+{% else %}
+ExecStart=/usr/bin/dockerd {% if docker_enable_tcp_socket %} -H tcp://{{ docker_tcp_socket_host }}:{{ docker_tcp_socket_port }} {% endif %} -H fd:// --containerd=/run/containerd/containerd.sock
+{% endif %}