What components are included in creating a Docker image using a Dockerfile?

When creating a Docker image using a Dockerfile, the following main components are included:

• Base image (FROM) — the source image on which the new one is built, for example, python:3.9.
• Copying files (COPY or ADD) — adding source code, dependencies, and other resources into the image.
• Installing dependencies (RUN) — executing commands to install libraries, packages, and more, for example, pip install.
• Setting environment variables (ENV) — establishing environment variables.
• Defining the working directory (WORKDIR) — specifying the directory where commands will be executed.
• Startup command (CMD or ENTRYPOINT) — determines which command will run when the container starts.

Example Dockerfile for a Python application:

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