Part1: Containerize an application

10/16/2025 · 2 min read

For the rest of this guide, you’ll be working with a simple todo list manager that runs on Node.js.

Get the app

$ git clone https://github.com/docker/getting-started-app.git

Build the app’s image

To build the image, you’ll need to use a Dockerfile. Docker uses this script to build a container image.

# syntax=docker/dockerfile:1

FROM node:lts-alpine
WORKDIR /app
COPY . .
RUN yarn install --production
CMD ["node", "src/index.js"]
EXPOSE 3000

In the terminal, make sure you're in the getting-started-app directory.

$ cd /path/to/getting-started-app
$ docker build -t getting-started .

The docker build command uses the Dockerfile to build a new image. After Docker downloaded the image node:lts-alphine, the instructions from the Dockerfile copied in your application and used yarn to install your application’s dependencies. The CMD directive specifies the default command to run when starting a container from this image.

Finally, the -t flag tags your image. Think of this as a human-readable name for the final image. Since you named the image getting-started, you can refer to that image when you run a container.

The . at the end of the docker build command tells Docker that it should look for the Dockerfile in the current directory.

Start an app container

Now that you have an image, you can run the application in a container using the docker run command.

Run your container using the docker run command and specify the name of the image you just created:

$ docker run -d -p 127.0.0.1:3000:3000 getting-started

The -d flag (short for —detach) runs the container in the background. This means that Docker starts your container and returns you to the terminal prompt. Also, it does not display logs in the terminal.

Part 2: Update the application Part 3: Share the application Part 4: Persist the DB Part 5: Use bind mounts Part 5: Multi-container apps Part 7: Use Docker Compose Part 8: Image-building best practices Part 9: What next Educational resources

Link: docker official website docs.docker.com Containerize an application.