What is a Dockerfile?

In a nutshell

The Dockerfile is a plain text file that contains all the commands needed to build a Docker image.

Example Dockerfile

# Specify base image
FROM ruby:3.2-slim

# Set the working directory in Docker
WORKDIR /app

# Copy the content of the local src directory to the working directory
COPY . .

# Specify the command to run on container start
CMD ["ruby", "./hello-docker.rb"]