Added warning about container, image and volume removals

README.md

@@ -3,6 +3,11 @@ This image will periodically clean up exited containers and remove images and vo
 running container. Based on [tutumcloud/image-cleanup](https://github.com/tutumcloud/image-cleanup) and
 [chadoe/docker-cleanup-volumes](https://github.com/chadoe/docker-cleanup-volumes) with some small fixes.
 
+**WARNING: This script will remove all exited containers, data-only containers and unused images unless you 
+carefully exclude them. Take care if you mount /var/lib/docker into the container since that will clean 
+up all unused data volumes. If it's not compatible with your system or Docker version it may delete 
+all your volumes, even from under running containers.**
+
 Normally any Docker containers that exit are still kept on disk until *docker rm -v* is used to clean
 them up. Similarly any images that aren't used any more are kept around. For a cluster node that see
 lots of containers start and stop, large amounts of exited containers and old image versions can fill