FROM | FROM ubuntu:20.04 | Specifies the base image |
RUN | RUN apt-get update && apt-get install -y python3 | Executes a command in the shell during the build process |
COPY | COPY . /app | Copies files from the host to the container |
ADD | ADD https://example.com/file.tar.gz /app/ | Similar to COPY but can also retrieve remote files and unpack archives |
WORKDIR | WORKDIR /app | Sets the working directory for the RUN, CMD, ENTRYPOINT, COPY and ADD instructions |
CMD | CMD ["python3", "app.py"] | Provides the default command to run the container |
ENTRYPOINT | ENTRYPOINT ["python3", "app.py"] | Configures the container to run as an executable |
ENV | ENV APP_ENV=production | Sets environment variables |
EXPOSE | EXPOSE 80 | Informs Docker that the container listens on the specified network ports at runtime |
VOLUME | VOLUME /data | Creates a mount point with the specified path and marks it as holding externally mounted volumes |
USER | USER appuser | Sets the user name or UID to use when running the image |
LABEL | LABEL version="1.0" | Adds metadata to the image |
ARG | ARG VERSION=1.0 | Defines a variable that users can pass at build-time to the builder with the docker build command |
ONBUILD | ONBUILD RUN apt-get update | Adds a trigger instruction to be executed when the image is used as a base for another build |
STOPSIGNAL | STOPSIGNAL SIGKILL | Sets the system call signal that will be sent to the container to exit |
HEALTHCHECK | HEALTHCHECK –interval=30s CMD curl –fail http://localhost | Tells Docker how to test that the container is still working |
