Note: Environment persistence can cause unexpected side effects. For example, setting ENV DEBIAN_FRONTEND noninteractive may confuse apt-get users on a Debian-based image. To set a value for a single command, use RUN <key>=<value> <command>.

The environment variables set using ENV will persist when a container is run from the resulting image. You can view the values using docker inspect, and change them using docker run --env <key>=<value>.