FROM — specifies the base (parent) image.
LABEL —provides metadata. Good place to include maintainer info.
ENV — sets a persistent environment variable.
RUN —runs a command and creates an image layer. Can be used to install packages into containers or run specific commands(i.e mkdir and etc.).
COPY — copies files and directories to the container.
ADD — copies files and directories to the container. Can upack local .tar files.
CMD — provides a command and arguments for an executing container. Parameters can be overridden. There can be only one CMD.
WORKDIR — sets the working directory for the instructions that follow.
ARG — defines a variable to pass to Docker at build-time.
ENTRYPOINT — provides command and arguments for an executing container. Arguments persist.
EXPOSE — exposes a port.
VOLUME — creates a directory mount point to access and store persistent data.
Note Only the instructions FROM, RUN, COPY, and ADD create layers in the final image.