working and tested daemon.json settings

defaults/main.yml

@@ -4,6 +4,10 @@ docker_edition: 'ce'
 docker_package: "docker-{{ docker_edition }}"
 docker_package_state: present
 
+# Docker daemon settings (generates /etc/docker/daemon.json)
+# docker_daemon_settings: 
+# root-dir: "/data/"
+
 # Service options.
 docker_service_state: started
 docker_service_enabled: true

tasks/main.yml

@@ -11,6 +11,14 @@
     state: "{{ docker_package_state }}"
   notify: restart docker
 
+- name: Configure /etc/docker/daemon.json
+  template:
+    src: daemon.json.j2
+    dest: /etc/docker/daemon.json
+    mode: 0640
+  when: docker_daemon_settings is defined
+  notify: restart docker
+
 - name: Ensure Docker is started and enabled at boot.
   service:
     name: docker

templates/daemon.json.j2

@@ -0,0 +1 @@
+{{ docker_daemon_settings | to_nice_json() }}