Question
I'm confused about when should I use CMD vs RUN. For example, to execute
bash/shell commands (i.e. ls -la) I would always use CMD or is there a
situation where I would use RUN? Trying to understand the best practices
about these two similar Dockerfile directives.
Answer
RUN is an image build
step, the state of the container after a RUN command will be committed to
the container image. A Dockerfile can have many RUN steps that layer on top
of one another to build the image.
CMD is the command
the container executes by default when you launch the built image. A
Dockerfile will only use the final CMD defined. The CMD can be overridden
when starting a container with docker run $image $other_command.
ENTRYPOINT is
also closely related to CMD and can modify the way a CMD is interpreted
when a container is started from an image.
