Persist container data

This walkthrough shows you how to persist data between containers. To better understand some concepts in this walkthrough, complete the Run multi-container applications walkthrough first.

Docker isolates all content, code, and data in a container from your local filesystem. When you delete a container, Docker deletes all the content within that container.

Sometimes, you may want to persist the data that a container generates. To do this, you can use volumes.

Step 1: Get the sample application

If you have git, you can clone the repository for the sample application. Otherwise, you can download the sample application. Choose one of the following options.

$ git clone https://github.com/docker/multi-container-app

Step 2: Add a volume to persist data

To persist data after you delete a container, use a volume. A volume is a location in your local filesystem, automatically managed by Docker Desktop.

To add a volume to this project, open the compose.yaml file in a code or text editor, and then uncomment the following lines.

todo-database:
    # ...
    volumes:
      - database:/data/db

# ...
volumes:
  database:

The volumes element that is nested under todo-database tells Compose to mount the volume named database to /data/db in the container for the todo-database service.

The top-level volumes element defines and configures a volume named database that can be used by any of the services in the Compose file.

Step 3: Run the application

To run the multi-container application, open a terminal and run the following commands. Replace /path/to/multi-container-app/ with the path to your application's directory.

Tip

To run Docker commands, you must use a terminal. Based on your operating system, you can open a terminal by doing the following:

For Windows, select the Start Menu, specify cmd, and then select Command Prompt.

For Mac, select the Launchpad icon in the Dock, specify Terminal in the search field, then select Terminal.

$ cd /path/to/multi-container-app/

$ docker compose up -d

Step 4: View the frontend and add todos

In the Containers tab of Docker Desktop, you should now have an application stack with two containers running (the todo-app, and todo-database).

To view the frontend and add todos:

1. In Docker Desktop, expand the application stack in Containers.
2. Select the link to port 3000 in the Port(s) column or open http://localhost:3000⁠.
3. Add some todo tasks in the frontend.

Step 5: Delete the application stack and run new containers

Now, no matter how often you delete and recreate the containers, Docker Desktop persists your data and it's accessible to any container on your system by mounting the database volume. Docker Desktop looks for the database volume and creates it if it doesn't exist.

To delete the application stack:

1. Open the Containers tab of Docker Desktop
2. Select the Delete icon next to your application stack.

After you delete the application stack, follow the steps from Step 3: Run the application to run the application again. Note that when you delete the containers and run them again, Docker Desktop persists any todos that you created.

Summary

In this walkthrough, you persisted data between containers using a volume. You can use this to persist and share data among isolated and ephemeral containers.

Related information:

• Deep dive into volumes
• Learn about using volumes in Compose in the Compose file reference
• Explore using volumes via the CLI in the docker volume CLI reference and Docker run reference

Next steps

Continue to the next walkthrough to learn how you can access a local directory from a container.