[Docker: Dockerfile] Syntax to build an image #docker

Dockerfile

# Argument outside the build stage
# To be used in first FROM
ARG <key>=<value>

# Parent image
FROM [--platform=<platform>] <image> [AS <name>]
# or
FROM [--platform=<platform>] <image>[:<tag>] [AS <name>]
# or
FROM [--platform=<platform>] <image>[@<digest>] [AS <name>]

# Set the working directory
# Create it if it doesn't exist
WORKDIR /foo

# Run a command and commit the result
RUN <command>
# or, parsed as json (use "" and escape characters)
RUN ["executable", "param1", "param2"]
# or, creating a bind mount
# https://docs.docker.com/engine/reference/builder/#run---mount
RUN --mount=[type=<TYPE>][,option=<value>[,option=<value>]...]

# Default command when executing a container
# This can be overridden by cli `docker run` arguments
# exec form, this is the preferred form
CMD ["executable","param1","param2"] 
# or, as default parameters to ENTRYPOINT
CMD ["param1","param2"] 

# Indicate a port intended to be published
# `docker run -P` will publish all exposed ports
EXPOSE <port>[/<protocol>]

# Set environment variable that persists in running container
# This can be overridden by `docker run --env <key>=<value>`
ENV <key>=<value>

# To not persist a variable into container, use an ARG
ARG DEBIAN_FRONTEND=noninteractive
RUN apt-get update && apt-get install -y ...

# Copy files to image's filesystem
COPY <src> <dest>
# Copy from previous build stage
COPY --from=<name> <src> <dest>

# Copy files with more options
# https://docs.docker.com/engine/reference/builder/#add
ADD <src> <dest>

# Create a mount point
VOLUME <name>

# Configure container to run as executable
# Can be overridden with `docker run --entrypoint`
# additional cli args will override any CMD args
ENTRYPOINT ["node", "index.js"]

# Note: May be wise to dumb-init first, for PID 1
# https://github.com/Yelp/dumb-init
RUN apt install dumb-init
# then...
ENTRYPOINT [ "/usr/bin/dumb-init", "--" ]
# start your actual command
CMD [ "node", "index.js" ]