Should I be concerned about excess, non-running, Docker containers?

Question

Every docker run command, or every RUN command inside a Dockerfile, creates a container. If the container is no longer running it can still be seen wit

Answer 1

The containers that are not running are not taking any system resources besides disk space.

It is usually good to clean up after yourself, but if you have a lot of them sitting around it shouldn't slow down performance at all.

If you do notice a slow down when running docker commands with lots of stopped containers, it might be a bug in docker, and you should submit a bug.