Docker file note

Certainly, here are all the commonly used Dockerfile commands along with detailed explanations:

  1. FROM:

    • Specifies the base image to use as the starting point for your Docker image.

    • Usage: FROM image:tag

    • Example: FROM ubuntu:latest

  2. RUN:

    • Executes shell commands within the image during the build process. Typically used for installing software, updating packages, or any setup tasks.
    • Usage: RUN command
    • Example: RUN apt-get update && apt-get install -y python3

  3. COPY:

    • Copies files or directories from the host machine into the image. It's often used to add application code and resources to the image.
    • Usage: COPY source destination
    • Example: COPY app.py /app/

  4. WORKDIR:

    • Sets the working directory inside the container where subsequent commands will be executed. Useful for organizing files and specifying paths.
    • Usage: WORKDIR path
    • Example: WORKDIR /app

  5. EXPOSE:

    • Informs Docker that the container will listen on specific ports at runtime. It doesn't actually expose the ports; it's for documentation purposes.
    • Usage: EXPOSE port(s)
    • Example: EXPOSE 8080

  6. CMD:

    • Specifies the default command to run when a container is started from the image. You can override it when starting a container.
    • Usage: CMD ["executable", "param1", "param2"]
    • Example: CMD ["python3", "app.py"]

  7. ENTRYPOINT:

    • Similar to CMD, it defines the default command to run when a container starts, but it's more rigid and doesn't allow command override. Useful for creating containerized applications that act like executables.
    • Usage: ENTRYPOINT ["executable", "param1", "param2"]
    • Example: ENTRYPOINT ["python3", "app.py"]

  8. ENV:

    • Sets environment variables within the container. These variables can be used in subsequent Dockerfile commands or by the running application.
    • Usage: ENV key=value
    • Example: ENV MY_VARIABLE=value

  9. VOLUME:

    • Creates a mount point for external volumes or data to be shared with the container. It allows data persistence and sharing between containers.
    • Usage: VOLUME /path
    • Example: VOLUME /data

  10. USER:

    • Sets the user or UID (User ID) under which the container will run. It's useful for improving security by running processes with lower privileges.
    • Usage: USER username_or_UID
    • Example: USER appuser