Dockerfile CMD instruction will exit the container just after running it

A docker container will run as long as the CMD from your Dockerfile takes.

In your case your CMD consists of a shell script containing a single echo. So the container will exit after completing the echo.

You can override CMD, for example:

sudo docker run -it --entrypoint=/bin/bash <imagename>

This will start an interactive shell in your container instead of executing your CMD. Your container will exit as soon as you exit that shell.

If you want your container to remain active, you have to ensure that your CMD keeps running. For instance, by adding the line while true; do sleep 1; done to your shell.sh file, your container will print your hello message and then do nothing any more until you stop it (using docker stop in another terminal).

You can open a shell in the running container using docker exec -it <containername> bash. If you then execute command ps ax, it will show you that your shell.sh is still running inside the container.

Finally with some experiments I got my best result as below

There is nothing wrong with my Dockerfile as below it's correct.

FROM ubuntu:14.04

ADD shell.sh /usr/local/bin/shell.sh

RUN chmod 777 /usr/local/bin/shell.sh

CMD /usr/local/bin/shell.sh

What I do to get expected result is, I just add one more command(/bin/bash) in my shell script file as below and vola everything works in my best way.

#!/bin/bash

echo “Hello-docker” > /usr/hello.txt

/bin/bash