Summarize this article with:
Your application works on your machine. It breaks in production. Sound familiar?
Learning how to create a Docker container solves this problem by packaging your code, dependencies, and runtime into one portable unit.
Containers run the same everywhere. Your laptop, a test server, the cloud. No more “works on my machine” excuses.
This guide walks you through the complete containerization process step by step.
You will install Docker, write a Dockerfile, build your first image, and run a container in under 15 minutes.
No prior Docker experience required. Just basic command line skills and a working computer.
How to Create a Docker Container
Creating a Docker container is the process of packaging an application with its dependencies into an isolated, runnable instance using the Docker platform.
Developers need this when deploying applications consistently across different environments, testing software in isolation, or building microservices architectures.
This guide covers 6 steps requiring 10-15 minutes and basic command line knowledge.
Prerequisites
Before you start, make sure you have these ready:
- Docker Desktop 4.x (Windows/macOS) or Docker Engine 24.x (Linux)
- 4GB RAM minimum, 8GB recommended
- 20GB free disk space
- Administrator or sudo access
- Terminal or command prompt access
- A text editor (VS Code, Sublime, or similar)
New to containerization in development? You will still be able to follow along.
The steps work on Windows, macOS, and Linux with minor path differences.
Step One: How Do You Install and Verify Docker on Your System?
Run docker --version in your terminal to confirm Docker is installed and check the current version number.
If you see version 24.x.x or higher, you are ready to proceed. A “command not found” error means Docker is not installed yet.
Action
Open Terminal (macOS/Linux) or Command Prompt (Windows).
Type: docker --version
Expected output: Docker version 24.0.7, build afdd53b
Need to set up Docker first? Check out how to install Docker on your operating system.
Verify the Docker Daemon
Run docker info to check if the Docker daemon is running.
You should see details about containers, images, and server version. If you get a connection error, start Docker Desktop or run the daemon manually.
Purpose
Verification prevents failed builds later. The Docker CLI needs a running daemon to execute any container commands.
Step Two: Where Do You Create a Project Directory for Your Container?
Create a dedicated folder for your container project files, including the Dockerfile and application code.
This directory becomes the build context that Docker uses when creating your image.
Action
Run these commands in your terminal:
mkdir my-docker-app && cd my-docker-app
Verify your location with pwd (macOS/Linux) or cd (Windows).
Your project folder is now ready for the Dockerfile and application files.
Directory Structure
A typical container project looks like this:
my-docker-app/(root folder)Dockerfile(no extension)app.pyorindex.js(your application)requirements.txtorpackage.json(dependencies)
Keep your codebase organized from the start. Messy folder structures cause build failures.
Purpose
Docker needs a clean build context. Everything in this directory gets sent to the Docker daemon during the build process.
Step Three: How Do You Write a Dockerfile for Your Application?
Create a file named Dockerfile (no extension) containing instructions that tell Docker how to build your Docker image.
Each instruction adds a layer to the final image.
Action
Create the Dockerfile:
touch Dockerfile (macOS/Linux) or create a new file in your editor (Windows).
Open it and add your instructions. The file must be named exactly Dockerfile with a capital D.
Basic Dockerfile Structure
Every Dockerfile needs these core instructions:
FROM– specifies the base image (python:3.11-slim, node:22-alpine)WORKDIR– sets the working directory inside the containerCOPY– transfers files from host to containerRUN– executes commands during image buildCMD– defines the default command when container starts
Example Dockerfile
Here is a simple Python application Dockerfile:
“ FROM python:3.11-slim WORKDIR /app COPY . . RUN pip install --no-cache-dir -r requirements.txt CMD ["python", "app.py"] `
The base image selection matters. Alpine images are smaller but may lack some packages. Slim images balance size and compatibility.
Dockerfile Instruction Reference
- FROM
- pulls the starting image from Docker Hub or another registry
- WORKDIR
- creates and switches to the specified directory
- COPY
- syntax isCOPY [source] [destination]
- RUN
- installs dependencies, runs setup scripts
- EXPOSE
- documents which ports the container listens on
- CMD
- only one CMD per Dockerfile, last one wins
- ENV
- sets environment variables
Purpose
The Dockerfile is your container blueprint. It makes builds repeatable and shareable across your team.
Version control your Dockerfile with Git just like any other code.
FAQ on How To Create A Docker Container
What is the difference between a Docker image and a container?
A Docker image is a read-only template containing your application code and dependencies.
A Docker container is a running instance of that image. Think of images as classes and containers as objects in programming.
Do I need Linux to create Docker containers?
No. Docker Desktop runs on Windows and macOS using a lightweight Linux VM in the background.
Your containers still use Linux internally, but you can build and run them from any operating system.
What is a Dockerfile and why do I need one?
A Dockerfile is a text file with instructions for building your container image. It specifies the base image, dependencies, and startup commands.
Without it, you cannot automate your container builds.
How do I choose the right base image?
Match the base image to your application runtime. Use python:3.11-slim for Python apps, node:22-alpine for Node.js.
Alpine images are smaller. Slim images offer better compatibility.
Can I create a container without a Dockerfile?
Yes. Run docker run -it ubuntu bash to create a container interactively.
However, this approach is not reproducible. Dockerfiles let you version control and share your configuration management setup.
How do I access my application running inside a container?
Use port mapping with the -p flag. Running docker run -p 8080:80 myapp maps host port 8080 to container port 80.
Access your app at localhost:8080 in your browser.
What happens to my data when a container stops?
Container data is lost when the container is removed. Use Docker volumes to persist data beyond the app lifecycle.
Check where Docker volumes are stored on your system.
How do I stop a running Docker container?
Run docker stop containername for a graceful shutdown. Use docker kill for immediate termination.
Learn more about how to stop Docker containers properly.
Can I run multiple containers from the same image?
Yes. Each docker run command creates a new container instance from your image.
This is how you scale applications. For complex setups, use Docker Compose to manage multiple containers.
How do I troubleshoot a container that exits immediately?
Check logs with docker logs containerid. Common causes include missing dependencies, wrong CMD syntax, or application errors.
Run interactively with docker run -it myimage sh to debug inside the container.
Conclusion
You now know how to create a Docker container from scratch. The process is straightforward once you understand the core concepts.
Install Docker, write a Dockerfile, build an image, run a container. That is the entire workflow.
Containers change how teams ship software. No more environment mismatches. No more dependency conflicts.
Your next steps? Explore container registries to store and share your images.
Learn continuous integration to automate your container builds with every code push.
Set up continuous deployment pipelines to ship containers to production automatically.
Consider Kubernetes vs Docker for orchestrating multiple containers at scale.
The Docker CLI commands you learned today form the foundation of modern DevOps practices.
Start small. Containerize one application. Then expand from there.
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Over the years, he's worked with a range of clients and contributed to design publications like Design Your Way, Designmodo, WebDesignerDepot, WPDean, and Speckyboy, and Slider Revolution among others.
