If you have a container that won't finish a build or that it's not running for whatever reason, and you want to run it and poke around, you can use the following command:

$ docker run -ti --entrypoint /bin/bash <image-id>

You can get the image id by doing a docker ps -a:

$ docker ps -a
CONTAINER ID        IMAGE               COMMAND                  CREATED             STATUS                        PORTS               NAMES
ababfbf9eca6        4b57933639c0        "/bin/sh -c 'npm inst"   11 seconds ago   Exited (137) 11 seconds ago                       insane_bardeen

So, our command would look like:

$ docker run -ti --entrypoint /bin/bash 4b57933639c0