Is it mandatory to specify the entry point in the Dockerfile for container build?

No, specifying an entry point (ENTRYPOINT or CMD) in the Dockerfile is not mandatory for building the container. However, without them, the container will not know which command to execute by default when it starts.

If the entry point is not specified, you need to explicitly pass a command when starting the container, otherwise, the container will exit immediately.

Example of a minimal Dockerfile without an entry point:

FROM alpine
RUN echo "Hello, world!"

This container can be run with the command:

docker run <image> echo "Hi"

But if no command is specified at runtime, the container will simply exit.