Dockerfile reference

Commands	Description
COPY	Copy files in to the image
Volume	Creates a Mountpoint as defined
ENTRYPOINT	The executable that runs when container is run. It accepts input parameters, or takes from CMD
CMD	Command to execute at start, will ignore input parameters. If ENTRYPOINT is defined CMD arguments are passed as arguments. Only 1 command allowed, only last one will take effect.
EXPOSE	Defines ports to be published.
ENV	Variables to be defined in the container.
RUN	A command to be run in a new layer of Image being build
FROM	Define base image from which image is built. This is first instruction.
WORKDIR	Working Directory of container

Difference between CMD and ENTRYPOINT

Both Entry point and CMD execute instructions at start of container, however behaviour differ. CMD : When only CMD is specified, it executes command and will ignore any parameters passed. ENTRYPOINT: Defines command to execute at start, then inputs are passed as arguments. If CMD also specified, ENTRYPOINT will treat CMD as arguments than commands.

Use of CMD is preferred unless there is requirement to accept arguments for container run.