Add the possibility to customize the options in '/etc/docker/daemon.json'.

README.md

@@ -19,6 +19,16 @@ Available variables are listed below, along with default values (see `defaults/m
 
 The `docker_edition` should be either `ce` (Community Edition) or `ee` (Enterprise Edition). You can also specify a specific version of Docker to install using the distribution-specific format: Red Hat/CentOS: `docker-{{ docker_edition }}-<VERSION>`; Debian/Ubuntu: `docker-{{ docker_edition }}=<VERSION>`.
 
+You can customize `daemon configuration` by providing `daemon.json` values in yaml format. Example:
+
+    docker_config_options:
+      exec-opts:
+        - native.cgroupdriver=systemd
+      log-driver: journald
+      max-concurrent-downloads: 7
+      max-concurrent-uploads: 5
+      storage-driver: overlay2
+
 You can control whether the package is installed, uninstalled, or at the latest version by setting `docker_package_state` to `present`, `absent`, or `latest`, respectively. Note that the Docker daemon will be automatically restarted if the Docker package is updated. This is a side effect of flushing all handlers (running any of the handlers that have been notified by this and any other role up to this point in the play).
 
     docker_service_state: started

defaults/main.yml

@@ -9,6 +9,11 @@ docker_service_state: started
 docker_service_enabled: true
 docker_restart_handler_state: restarted
 
+# Docker config options.
+docker_config_options:
+  max-concurrent-downloads: 5
+  max-concurrent-uploads: 5
+
 # Docker Compose options.
 docker_install_compose: true
 docker_compose_version: "1.25.4"

tasks/main.yml

@@ -11,6 +11,17 @@
     state: "{{ docker_package_state }}"
   notify: restart docker
 
+- name: Ensure /etc/docker exists
+  file:
+    path: /etc/docker
+    state: directory
+
+- name: Install daemon.json
+  template:
+    src: docker-daemon.json.j2
+    dest: /etc/docker/daemon.json
+  notify: restart docker
+
 - name: Ensure Docker is started and enabled at boot.
   service:
     name: docker

templates/docker-daemon.json.j2

@@ -0,0 +1 @@
+{{ docker_config_options | default([])| to_nice_json }}