Difference between RUN and CMD in a docker file and when to use one or the other

Question

Which command to use to execute bash/shell commands i.e. ls -la.

When should I use CMD and where should I use RUN? 

What's the best practice about these two similar Dockerfile directives.

Can anyone help me with this?

Thanks.

Answer 1

Here are the explanations for all the three commands i.e., RUN,CMD and ENTRYPOINT.

RUN :-  A Dockerfile can have many RUN steps that layer on top of one another to build the image.

CMD :- It is the command which the container executes by default when you launch the built image. A Dockerfile can only have one CMD. The CMD can be overridden when starting a container with docker run $image $other_command.

ENTRYPOINT :- It is very much similar to CMD and can modify the way a container starts an image.

I hope that the above explanation will resolve your doubts.