What are the main instructions that make up a Dockerfile?

The main instructions of a Dockerfile include:

• FROM — specifies the base image to start the build.
• RUN — executes commands in the container during build (e.g., installing packages).
• COPY and ADD — copy files from the build context into the image.
• CMD — sets the default command to run when the container starts.
• ENTRYPOINT — sets the main executable for the container.
• ENV — sets environment variables.
• WORKDIR — sets the working directory for subsequent instructions.
• EXPOSE — declares the ports the container listens on.
• VOLUME — declares mount points for volumes.

Example Dockerfile for a Python application:

FROM python:3.9-slim
WORKDIR /app
COPY requirements.txt ./
RUN pip install -r requirements.txt
COPY . .
CMD ["python", "app.py"]