How to keep Docker container running after starting services

Question

Although I've read many instructions that appear to do what I'm trying to do, for some reason my Docker containers keep failing. In essence, I'm configuring a Docker container to house a web server and a few daemons. In my Dockerfile, I run a bash script called run-all.sh through CMD to complete the remaining steps. run-all. Sh appears as follows:

service supervisor start
service nginx start

And I start it inside of my Dockerfile as follows:

CMD ["sh", "/root/credentialize_and_run.sh"]

When I run things manually (by connecting to the image with -i -t /bin/bash), I can see that all of the services start up properly. When I run the image, however, it exits after starting up my processes. According to my understanding, for the processes to continue operating indefinitely, the container must remain active. But when I use docker ps -a, I observe:

➜  docker_test  docker ps -a
CONTAINER ID        IMAGE                            COMMAND                CREATED             STATUS                      PORTS               NAMES
c7706edc4189        some_name/some_repo:blah   "sh /root/run-all.sh   8 minutes ago       Exited (0) 8 minutes ago                        grave_jones

How come? Why is that happening? What's the proper technique to prevent my bash script from exiting? I know I could just add a while loop to the end of it to keep it going.