What are the most common instructions in Dockerfile?

The most common instructions in a Dockerfile are essential for defining the steps to build a Docker image. Here are the key instructions:

1. FROM: This instruction sets the base image for the Docker image being built. It is typically the first instruction in a Dockerfile.

   FROM ubuntu:20.04

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2. RUN: This instruction executes commands in a new layer on top of the current image and commits the results. It is often used to install software packages.

   RUN apt-get update && apt-get install -y python3

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3. CMD: This instruction provides the default command to run when a container is started from the image. Only the last CMD instruction in the Dockerfile is used.

   CMD ["python3", "app.py"]

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4. COPY: This instruction copies files or directories from the host machine into the Docker image.

   COPY . /app

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5. ADD: Similar to COPY, but with additional features like extracting tar files and fetching files from URLs.

   ADD myfile.tar.gz /app

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6. WORKDIR: This instruction sets the working directory for any subsequent instructions in the Dockerfile.

   WORKDIR /app

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7. EXPOSE: This instruction informs Docker that the container listens on the specified network ports at runtime.

   EXPOSE 8080

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8. ENV: This instruction sets environment variables.

   ENV APP_ENV=production

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9. ENTRYPOINT: This instruction configures a container that will run as an executable.

   ENTRYPOINT ["python3", "app.py"]

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10. VOLUME: This instruction creates a mount point with the specified path and marks it as holding externally mounted volumes from native host or other containers.

    VOLUME /data

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11. LABEL: This instruction adds metadata to an image in ...