How to automatically update your docker containers, if base-images are updated

Say I have a trivial container based on the ubuntu:latest. Now there is a security update and ubuntu:latest is updated in the docker repo .

1. How would I know my local image and its containers are running behind?

2. Is there some best practice for automatically updating local images and containers to follow the docker repo updates, which in practice would give you the same niceties of having unattended-upgrades running on a conventional ubuntu-machine