Right now, it is hard to know when the last time an image was used by a container, so when you need to do some image cleanup, you have to either guess, or track that data outside of docker.

It would be nice if we add a new attribute for the docker images command that showed the last time the image was used, so that we can use that when running a image clean up job. Ideally the timestamp would follow the whole image hierarchy and not just the last image on the tree, but it's parents, grandparents, etc.

I'm not sure when the image last_update is set, when the container is started, or stopped, but probably, best to update both times.