Last time I checked, there wasn’t a specific docker command for this
I use a few useful alias
alias docker_clean_images='docker rmi $(docker images -a --filter=dangling=true -q)'
alias docker_clean_ps='docker rm $(docker ps --filter=status=exited --filter=status=created -q)'
The first one cleans all dangling images. This is useful for removing intermediate images left over from multiple builds. The second one is for removing stopped containers. These are aliases I use for routine maintenance
If you want to remove ALL of your cache, you first have to make sure all containers are stopped and removed, since you cannot remove an image in use by a container. So something similar
docker kill $(docker ps -q)
docker_clean_ps
docker rmi $(docker images -a -q)
This would kill and remove all images in your cache. Less recommended, you could wipe the /var/lib/docker dir and start docker over, but that’s hardly necessary just to clear the cache