docker run = new container (specify image name)
docker exec = run a command in an existing container
How to turn a docker run command into an interactive shell:
-it --entrypoint=/bin/sh
Note, you have to add that before the name of the image.
Cleanup images
To filter down the images and only clean those matching some-text, use:
docker images | grep some-text | awk '{ print $1 ":" $2}' | xargs docker rmi
Cleanup orphaned images
Sometimes images are orphaned, for example, if you tagged an image as latest, and then built a new image with that same tag. They will show up as <none> in docker images. They can be cleaned up using:
docker rmi $(docker images -f "dangling=true" -q)
List images by size
docker images --format '{{.Size}}\t{{.Repository}}' | sort -hr