automatically purge docker images

common/docker/tasks/main.yml

@@ -20,6 +20,8 @@
     dest: /etc/docker/daemon.json
   notify: restart docker
 
+- name: Cronjob to prune unused images  
+  cron: name="docker-prune" weekday="*" hour="5" minute="5" job="/usr/bin/docker system prune --all -f"
 
 - name: "Create internal Networks: {{ docker.internal_networks }}"
   docker_network: