Why docker container exits immediately

Question

I run a container in the background using

 docker run -d --name hadoop h_Service

it exits quickly. But if I run in the foreground, it works

Answer 1

I would like to extend or dare I say, improve answer mentioned by camposer

When you run

docker run -dit ubuntu

you are basically running the container in background in interactive mode.

When you attach and exit the container by CTRL+D (most common way to do it), you stop the container because you just killed the main process which you started your container with the above command.

Making advantage of an already running container, I would just fork another process of bash and get a pseudo TTY by running:

docker exec -it  /bin/bash