The best way to get access to a running Docker container is to use the exec-command
docker exec -it <container> /bin/bash. It drops you right into a console within your container. Unfortunately, on some images the terminal is not properly allocated and many commands which are meant to run with a console are not working correctly, e.g.
clear results in an error:
root@1e5cd194c97a:/# clear TERM environment variable not set.
The problem is caused by an invalid
$TERM environment variable:
root@1e5cd194c97a:/# echo $TERM dumb
And can be fixed easily by running following command:
Afterwards all console related commands work normally again. The issue is documented in a Github issue in the Docker repository.