Bootstrap your projects with Docker init

In may 2023, Docker announced a new command line docker init, that could simplify your life when creating new projects.

It is aimed to quickly generate Dockerfile and Docker-compose file for your projects, following the best practices pushed by the editor himself.

Let's see how it works, with a simple example, running on Flask.

Create the app

Create a my-api.py file :

#!/usr/bin/python3
from flask import Flask, jsonify

app = Flask(__name__)

@app.route("/")
def hello_world():
    return "API is running..."

@app.route("/users", methods=["GET"])
def caracters():
    return jsonify({
        "users": [
            "Luke",
            "Leia",
            "Han",
            "Chewi",
            "Darth",
            "Obi",
        ]
    })

if __name__ == '__main__':
    app.run(port=3000, debug=True)

And a requirements.txt file :

flask>=2.2.2
gunicorn

Generate the files

Execute docker init and answer the questions.

It will generate you the following files :

Dockerfile - The instructions to build your image

# syntax=docker/dockerfile:1

# Comments are provided throughout this file to help you get started.
# If you need more help, visit the Dockerfile reference guide at
# https://docs.docker.com/go/dockerfile-reference/

# Want to help us make this template better? Share your feedback here: https://forms.gle/ybq9Krt8jtBL3iCk7

ARG PYTHON_VERSION=3.12.4
FROM python:${PYTHON_VERSION}-slim as base

# Prevents Python from writing pyc files.
ENV PYTHONDONTWRITEBYTECODE=1

# Keeps Python from buffering stdout and stderr to avoid situations where
# the application crashes without emitting any logs due to buffering.
ENV PYTHONUNBUFFERED=1

WORKDIR /app

# Create a non-privileged user that the app will run under.
# See https://docs.docker.com/go/dockerfile-user-best-practices/
ARG UID=10001
RUN adduser \
    --disabled-password \
    --gecos "" \
    --home "/nonexistent" \
    --shell "/sbin/nologin" \
    --no-create-home \
    --uid "${UID}" \
    appuser

# Download dependencies as a separate step to take advantage of Docker's caching.
# Leverage a cache mount to /root/.cache/pip to speed up subsequent builds.
# Leverage a bind mount to requirements.txt to avoid having to copy them into
# into this layer.
RUN --mount=type=cache,target=/root/.cache/pip \
    --mount=type=bind,source=requirements.txt,target=requirements.txt \
    python -m pip install -r requirements.txt

# Switch to the non-privileged user to run the application.
USER appuser

# Copy the source code into the container.
COPY . .

# Expose the port that the application listens on.
EXPOSE 3000

# Run the application.
CMD gunicorn 'my-api:app' --bind=0.0.0.0:3000

.dockerignore - The files you don’t want to copy to your container

# Include any files or directories that you don't want to be copied to your
# container here (e.g., local build artifacts, temporary files, etc.).
#
# For more help, visit the .dockerignore file reference guide at
# https://docs.docker.com/go/build-context-dockerignore/

**/.DS_Store
**/__pycache__
**/.venv
**/.classpath
**/.dockerignore
**/.env
**/.git
**/.gitignore
**/.project
**/.settings
**/.toolstarget
**/.vs
**/.vscode
**/*.*proj.user
**/*.dbmdl
**/*.jfm
**/bin
**/charts
**/docker-compose*
**/compose.y*ml
**/Dockerfile*
**/node_modules
**/npm-debug.log
**/obj
**/secrets.dev.yaml
**/values.dev.yaml
LICENSE
README.md

README.Docker.md - The Readme associated to Docker elements

### Building and running your application

When you're ready, start your application by running:
`docker compose up --build`.

Your application will be available at http://localhost:3000.

### Deploying your application to the cloud

First, build your image, e.g.: `docker build -t myapp .`.
If your cloud uses a different CPU architecture than your development
machine (e.g., you are on a Mac M1 and your cloud provider is amd64),
you'll want to build the image for that platform, e.g.:
`docker build --platform=linux/amd64 -t myapp .`.

Then, push it to your registry, e.g. `docker push myregistry.com/myapp`.

Consult Docker's [getting started](https://docs.docker.com/go/get-started-sharing/)
docs for more detail on building and pushing.

### References
* [Docker's Python guide](https://docs.docker.com/language/python/)

compose.yaml - The file to execute Docker-compose

# Comments are provided throughout this file to help you get started.
# If you need more help, visit the Docker Compose reference guide at
# https://docs.docker.com/go/compose-spec-reference/

# Here the instructions define your application as a service called "server".
# This service is built from the Dockerfile in the current directory.
# You can add other services your application may depend on here, such as a
# database or a cache. For examples, see the Awesome Compose repository:
# https://github.com/docker/awesome-compose
services:
  server:
    build:
      context: .
    ports:
      - 3000:3000

# The commented out section below is an example of how to define a PostgreSQL
# database that your application can use. `depends_on` tells Docker Compose to
# start the database before your application. The `db-data` volume persists the
# database data between container restarts. The `db-password` secret is used
# to set the database password. You must create `db/password.txt` and add
# a password of your choosing to it before running `docker compose up`.
#     depends_on:
#       db:
#         condition: service_healthy
#   db:
#     image: postgres
#     restart: always
#     user: postgres
#     secrets:
#       - db-password
#     volumes:
#       - db-data:/var/lib/postgresql/data
#     environment:
#       - POSTGRES_DB=example
#       - POSTGRES_PASSWORD_FILE=/run/secrets/db-password
#     expose:
#       - 5432
#     healthcheck:
#       test: [ "CMD", "pg_isready" ]
#       interval: 10s
#       timeout: 5s
#       retries: 5
# volumes:
#   db-data:
# secrets:
#   db-password:
#     file: db/password.txt

Now you can launch your app

Directly on your machine :

pip install flask --user
flask --app my-api --debug run -p 3000

With Docker :

docker build -t my-api .
docker run -d -p 3000:3000 --name my-api my-api

With Docker-compose :

docker init
docker compose up --build

What about Podman ?

Nowadays, we can’t talk about Docker without mentioning it’s alternative Podman.

Both provide very similar commands overall, but the Init command is an exception.

Podman-init has a different purpose : it creates a new container from an image and prepares it to run as a Podman container.

Conclusion

Docker-init is a handy little utility integrated into the command-line.

Consider using it when you need to create new projects (or update old ones), it can save you a few precious minutes, while helping you to be compliant by following best practices.