docker-compose port/volume host / container syntax:
host_port:container_port , host_volume:container_volume

list all running containers
docker ps -a

command line in a running container
docker exec -it <containerID> bash

stop all running containers
docker stop $(docker ps -a -q)

rm all running containers
docker rm $(docker ps -a -q)

list all docker images
docker images

remove specific docker images:
docker rmi <image1> <image2>

copy file from current directory to running container
docker cp foo.txt containerID:/foo.txt

update all docker images (even if they are not running)
for image in $(docker images --format "{{.Repository}}:{{.Tag}}" | grep -v '<none>'); do docker pull $image; done;

Free extra space with a prune:
docker system prune --all --force --volumes

To remove dangling / old images that are just taking up space:
docker rmi $(docker images --filter "dangling=true" -q --no-trunc)

Remove all exited containers: docker rm $(docker ps -a -f status=exited -q)

Kubernetes K3S

Start K3s Service: systemctl start k3s.service

Stop K3s Service: systemctl stop k3s.service