Docker
Go inside a running container
docker exec -it <containerIdOrName> bash (or /bin/bash or /bin/ash)
Look inside an image
docker run -it --entrypoint /bin/bash <imageid>
Stop and remove all docker containers and images
Stop all running containers
docker stop $(docker ps -aq)
Remove all containers
docker rm $(docker ps -aq)
Remove all images
docker rmi $(docker images -q)
Clean
docker [image,container,volume,..] prune -a