Installation instructions taken from bastilimbach/docker-MagicMirror.

docker run  -d \
    --publish 80:8080 \   # NOTE: see below
    --restart always \
    --volume ~/magic_mirror/config:/opt/magic_mirror/config \
    --volume ~/magic_mirror/modules:/opt/magic_mirror/modules \
    --volume /etc/localtime:/etc/localtime:ro \
    --name magic_mirror \
    bastilimbach/docker-magicmirror

Regarding the publish kwarg:

• I was already running another web server, so I changed the publish port to 8080:8080, so that I could run it on a port independent of that other web server.