Docker is a software system for creating and running containers. There is an alternative that can work rootless called Podman.

Prune old docker files

docker system prune -a

Build and run a Dockerfile

docker run -it \
    -p 70:70 \
    -d \
    $(docker build -q .)

Container OS / CoreOS randomly kills my containers

You can prevent this by writing SystemD service files that restarts your containers when they die. In this scenario, SystemD acts as a watchdog. You can also observe the container states and logs via SystemD if you do this.