Prune the dangling images daily.

defaults/main.yml

@@ -12,6 +12,8 @@ docker_swarm_worker_hostname: '{{ ansible_fqdn }}'
 docker_swarm_allowed_hosts:
   - '0.0.0.0/0'
 
+docker_prune_dangling_images: true
+
 # Set this to one of the manager hostnames to be able to initialize the cluster
 docker_swarm_manager_main_node_hostname: localhost
 docker_swarm_manager_main_node_address: 127.0.0.1

files/docker-prune-dangling-images.sh

@@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+
+docker image prune --force > /var/log/docker-prune.log 2>&1
+exit 0

tasks/docker_setup.yml

@@ -40,6 +40,39 @@
   when: docker_install
   tags: [docker]
 
+- name: Cron job that prunes the dangling images
+  block:
+    - name: Install a script that prunes the docker dangling images
+      copy:
+        src: docker-prune-dangling-images.sh
+        dest: /usr/local/sbin/docker-prune-dangling-images
+        owner: root
+        group: root
+        mode: 0744
+
+    - name: Install a cron job that prunes the docker images
+      cron:
+        name: Prune docker images
+        cron_file: docker-prune-images
+        special_time: daily
+        user: root
+        state: present
+        job: "/usr/local/sbin/docker-prune-dangling-images"
+      when: docker_prune_dangling_images
+
+    - name: Disable the cron job that prunes the docker images
+      cron:
+        name: Prune docker images
+        cron_file: docker-prune-images
+        special_time: daily
+        user: root
+        state: absent
+        job: "/usr/local/sbin/docker-prune-dangling-images"
+      when: not docker_prune_dangling_images
+
+  when: docker_install
+  tags: [docker, docker_prune_images]
+
 - block:
     - name: Remove the docker user
       user: name=docker state=absent