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

My pracitce is in the Dockerfile start a shell which will not exit immediately CMD [ "sh", "-c", "service ssh start; bash"], then run docker run -dit image_name. This way the (ssh) service and container is up running.