Educational

Using Docker for Django Deployment

—

by

Saim Khalid
in

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Introduction

Modern web development requires consistency, scalability, and efficiency. One of the biggest challenges developers face is ensuring that an application runs identically in every environment — development, staging, and production.
Have you ever experienced an application that works perfectly on your local machine but fails when deployed to a server? This issue is often caused by differences in system configurations, dependencies, or environments.

Docker solves this problem by creating lightweight, portable containers that encapsulate your entire application — including code, dependencies, and environment settings.
In this guide, we’ll walk through how to Dockerize a Django application, create a Dockerfile, set up Docker Compose, and understand how to deploy Django using containers in a reliable and reproducible way.

1. What Is Docker?

Docker is an open-source platform that allows developers to automate the deployment of applications inside containers.
A container is a lightweight, standalone, and executable package that includes everything needed to run an application — code, runtime, system tools, and libraries.

In simple terms, Docker ensures that if your app runs on your computer, it will run the same way everywhere — on another developer’s machine, a cloud server, or in production.

Benefits of Using Docker for Django

  1. Consistency Across Environments:
    Avoid “it works on my machine” problems by having identical environments everywhere.
  2. Isolation:
    Each container is isolated from others, so your dependencies and configurations never clash.
  3. Simplified Deployment:
    Once a Docker image is built, you can deploy it anywhere with minimal effort.
  4. Scalability:
    Docker integrates easily with orchestration tools like Kubernetes and Docker Swarm for scaling.
  5. Portability:
    The same container can run on local, staging, and production servers without changes.

2. Preparing a Django Application for Docker

Before we start creating Docker configurations, make sure you have a Django project ready.

If you don’t have one, you can quickly create a sample Django app:

mkdir docker_django
cd docker_django
python -m venv venv
source venv/bin/activate
pip install django
django-admin startproject projectname .
python manage.py runserver

Once the project runs locally, we’re ready to containerize it.

3. Installing Docker and Docker Compose

You need to have both Docker Engine and Docker Compose installed.

Install Docker on Ubuntu

sudo apt update
sudo apt install docker.io -y

Enable and start Docker:

sudo systemctl enable docker
sudo systemctl start docker

Check if Docker is running:

docker --version

Install Docker Compose

sudo apt install docker-compose -y

Check version:

docker-compose --version

Once both are installed, we can begin building our Docker setup.

4. Understanding Docker Concepts

Before jumping into code, let’s quickly review key Docker concepts:

1. Dockerfile

A Dockerfile is a script containing instructions to build a Docker image.
It defines:

  • Base image (like python:3.10)
  • Dependencies to install
  • Files to copy into the image
  • Commands to run the application

2. Docker Image

A Docker image is the blueprint of your application environment. It’s built from a Dockerfile and can be reused anywhere.

3. Docker Container

A container is a running instance of a Docker image. It behaves like a lightweight, isolated virtual machine.

4. Docker Compose

A docker-compose.yml file defines multiple services (like your Django app, database, and cache) and how they interact.
It simplifies multi-container setups with one command.

5. Creating a Dockerfile for Django

Now we’ll create a Dockerfile at the root of your Django project.

FROM python:3.10

WORKDIR /app

COPY requirements.txt .

RUN pip install --no-cache-dir -r requirements.txt

COPY . .

CMD ["gunicorn", "projectname.wsgi:application", "--bind", "0.0.0.0:8000"]

Explanation of Each Line

  • FROM python:3.10
    Specifies the base image — in this case, Python 3.10.
    Docker uses this as the foundation for your container.
  • WORKDIR /app
    Sets /app as the working directory inside the container.
  • COPY requirements.txt .
    Copies your project’s requirements.txt file into the container.
  • RUN pip install –no-cache-dir -r requirements.txt
    Installs all dependencies listed in requirements.txt.
  • COPY . .
    Copies the rest of your Django project files into the container.
  • CMD [“gunicorn”, “projectname.wsgi:application”, “–bind”, “0.0.0.0:8000”]
    Defines the command that runs when the container starts — here, Gunicorn starts the Django app and binds it to port 8000.

6. Creating a Requirements File

Your Dockerfile refers to a requirements.txt file that lists all Python dependencies.

Create one if it doesn’t exist:

pip freeze > requirements.txt

Example content:

Django==4.2
gunicorn==21.2.0
djangorestframework==3.15.0

7. Building and Running the Docker Image

Now that your Dockerfile and requirements are ready, you can build your Docker image.

Step 1: Build the Image

Run this command in the project directory:

docker build -t django_app .

Here:

  • -t django_app names the image “django_app”.
  • The dot (.) tells Docker to use the current directory as the build context.

Step 2: Run the Container

Once the image is built:

docker run -d -p 8000:8000 django_app
  • -d runs the container in detached mode (in the background).
  • -p 8000:8000 maps port 8000 on your host to port 8000 inside the container.

Step 3: Test in Browser

Visit:

http://localhost:8000

If everything went well, you’ll see your Django application running — inside a Docker container.

8. Verifying Containers

You can verify that your container is running:

docker ps

Output example:

CONTAINER ID   IMAGE         COMMAND                  STATUS         PORTS
a1b2c3d4e5f6   django_app    "gunicorn projectnam…"   Up 10 minutes  0.0.0.0:8000->8000/tcp

To view logs:

docker logs a1b2c3d4e5f6

To stop the container:

docker stop a1b2c3d4e5f6

9. Using Docker Compose for Simplicity

When working with multiple containers (for example, Django + PostgreSQL), managing each individually becomes cumbersome.
Docker Compose allows you to define and run multi-container applications easily using a docker-compose.yml file.

Example docker-compose.yml

version: '3'

services:
  web:

build: .
command: gunicorn projectname.wsgi:application --bind 0.0.0.0:8000
ports:
  - "8000:8000"
volumes:
  - .:/app
depends_on:
  - db

  db:

image: postgres:14
environment:
  POSTGRES_USER: django
  POSTGRES_PASSWORD: django123
  POSTGRES_DB: djangodb

Explanation

  • web: Your Django container.
  • build: Builds from the Dockerfile in the current directory.
  • command: The startup command (Gunicorn).
  • ports: Maps port 8000 from the container to the host.
  • volumes: Syncs local files with the container for easy development.
  • depends_on: Ensures the database starts before the web service.
  • db: Uses a PostgreSQL container with environment variables for credentials.

10. Running Docker Compose

Start all services with one command:

docker-compose up --build

This will:

  1. Build the Docker image (if not already built)
  2. Create containers for web and database
  3. Run them together, linked automatically

Now open:

http://localhost:8000

Your Django app should connect to the PostgreSQL container seamlessly.

11. Connecting Django to PostgreSQL in Docker

In your Django settings.py, configure the database to match the PostgreSQL container credentials.

DATABASES = {

'default': {
    'ENGINE': 'django.db.backends.postgresql',
    'NAME': 'djangodb',
    'USER': 'django',
    'PASSWORD': 'django123',
    'HOST': 'db',
    'PORT': 5432,
}
}

Notice that HOST is set to db — the name of the database service defined in docker-compose.yml.
Docker Compose automatically handles internal DNS resolution between containers.

Then run:

docker-compose exec web python manage.py migrate

This applies migrations to the PostgreSQL container.

12. Serving Static Files in Docker

For production, Django needs static files collected.

Update your Dockerfile to include:

RUN python manage.py collectstatic --noinput

Ensure STATIC_ROOT is defined in settings.py:

STATIC_ROOT = BASE_DIR / 'staticfiles'

Now, when you build the image, static files will be collected automatically inside the container.

13. Environment Variables with Docker

Never hardcode secrets (like passwords or keys) inside your settings.
Use environment variables instead.

Step 1: Update docker-compose.yml

environment:
  - DEBUG=False
  - SECRET_KEY=mysecretkey
  - ALLOWED_HOSTS=*

Step 2: Use Them in settings.py

import os

SECRET_KEY = os.environ.get('SECRET_KEY')
DEBUG = os.environ.get('DEBUG', 'False') == 'True'
ALLOWED_HOSTS = os.environ.get('ALLOWED_HOSTS', '*').split(',')

You can also store them in a .env file and reference it in your Docker Compose file for security.

14. Managing Containers

Useful Docker commands:

docker-compose ps

List all running services.

docker-compose logs

View logs from all containers.

docker-compose down

Stop and remove containers, networks, and volumes.

docker-compose restart

Restart all containers.

These commands simplify your workflow compared to managing each container manually.

15. Using Gunicorn and Nginx Inside Docker

For production, you can extend your Docker setup to include Nginx as a reverse proxy in front of Gunicorn.

Example docker-compose.yml (with Nginx)

version: '3'

services:
  web:

build: .
command: gunicorn projectname.wsgi:application --bind 0.0.0.0:8000
volumes:
  - .:/app
expose:
  - "8000"
depends_on:
  - db

  db:

image: postgres:14
environment:
  POSTGRES_USER: django
  POSTGRES_PASSWORD: django123
  POSTGRES_DB: djangodb

  nginx:

image: nginx:latest
ports:
  - "80:80"
volumes:
  - ./nginx:/etc/nginx/conf.d
depends_on:
  - web

Nginx Configuration File (nginx/default.conf)

server {

listen 80;
server_name localhost;


location / {
    proxy_pass http://web:8000;
}


location /static/ {
    alias /app/staticfiles/;
}
}

This setup:

  • Uses Nginx to handle HTTP requests.
  • Passes dynamic requests to Gunicorn.
  • Serves static files directly.
  • Runs everything inside Docker containers.

16. Scaling with Docker Compose

To scale horizontally, you can run multiple web containers:

docker-compose up --scale web=3

This starts three containers running the Django app simultaneously.
You can then configure Nginx to load balance between them.

Scaling with Docker allows your Django app to handle higher traffic seamlessly.

17. Debugging Containers

If something doesn’t work, you can enter a container’s shell for debugging.

docker exec -it container_name /bin/bash

Inside the container, you can inspect logs, check configurations, or manually run Django commands.

Example:

python manage.py shell
python manage.py check

18. Deploying Dockerized Django to Production

Once your Docker setup works locally, deploying it to a production server is easy.

Step 1: Copy Files to Server

Use Git, SCP, or any CI/CD pipeline to push your files (Dockerfile, docker-compose.yml, code) to the server.

Step 2: Install Docker on Server

sudo apt install docker.io docker-compose -y

Step 3: Start the Application

docker-compose up -d --build

The -d flag runs containers in the background.

Your application is now live on the server — identical to your local setup.

19. Advantages of Docker Deployment

Let’s summarize why deploying Django with Docker is so effective:

  1. Predictable Environments
    Everything runs inside containers — no dependency conflicts.
  2. Fast Setup
    On any machine, docker-compose up starts your entire stack.
  3. Easy Rollbacks
    You can switch back to a previous image version instantly.
  4. Security
    Containers isolate applications and reduce attack surfaces.
  5. Continuous Integration
    Docker integrates well with CI/CD pipelines for automated builds and deployments.
  6. Cross-Platform
    Works identically on Windows, macOS, Linux, and cloud platforms like AWS, GCP, or Azure.

20. Troubleshooting Common Issues

Problem 1: ModuleNotFoundError for Django

Make sure requirements.txt is correctly copied and installed before the code files in the Dockerfile.

Problem 2: Database Connection Error

Ensure the database container name in Django’s settings matches the Compose service name (db).

Problem 3: Permission Denied on Static Files

Add correct permissions:

chmod -R 755 staticfiles

Problem 4: Docker Build Too Slow

Use caching by placing COPY requirements.txt . and RUN pip install before copying the full code.

Problem 5: Environment Variables Missing

Ensure variables are correctly set in docker-compose.yml or a .env file.

21. Using Docker in Development vs. Production

AspectDevelopmentProduction
DEBUG ModeTrueFalse
Static FilesServed by DjangoServed by Nginx
DatabaseSQLite or Postgres containerDedicated Postgres instance
LoggingConsole outputCentralized logging (e.g., ELK stack)
ScalingSingle containerMultiple containers, load balancing

You can maintain two different docker-compose files:

  • docker-compose.dev.yml
  • docker-compose.prod.yml

This separation allows fine-tuning for different environments.

22. Cleaning Up Docker Resources

Over time, Docker images and containers consume disk space.
Clean them up periodically:

docker system prune -a

This removes stopped containers, unused images, and dangling resources.

23. Continuous Deployment with Docker

Docker integrates seamlessly with CI/CD tools such as GitHub Actions, GitLab CI, or Jenkins.

Typical workflow:

  1. Code pushed to GitHub.
  2. CI pipeline builds a new Docker image.
  3. Image is pushed to Docker Hub or a private registry.
  4. Production server pulls the latest image and restarts containers.

This automates deployments and minimizes downtime.

24. Example: Minimal End-to-End Workflow

  1. Clone the repository: git clone https://github.com/yourusername/yourproject.git
  2. Build Docker image: docker build -t django_app .
  3. Run containers: docker-compose up -d
  4. Apply migrations: docker-compose exec web python manage.py migrate
  5. Collect static files: docker-compose exec web python manage.py collectstatic

Your Django app is now running in Docker — production-ready and portable.

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