Share the application

Table of contents

Now that you've built an image, you can share it. To share Docker images, you have to use a Docker registry. The default registry is Docker Hub and is where all of the images you've used have come from.

Docker ID

A Docker ID lets you access Docker Hub, which is the world's largest library and community for container images. Create a Docker ID for free if you don't have one.

Create a repository

To push an image, you first need to create a repository on Docker Hub.

  1. Sign up or Sign in to Docker Hub.

  2. Select the Create Repository button.

  3. For the repository name, use getting-started. Make sure the Visibility is Public.

  4. Select Create.

In the following image, you can see an example Docker command from Docker Hub. This command will push to this repository.

Docker command with push example

Push the image

  1. In the command line, run the docker push command that you see on Docker Hub. Note that your command will have your Docker ID, not "docker". For example, docker push YOUR-USER-NAME/getting-started.

    $ docker push docker/getting-started
The push refers to repository [docker.io/docker/getting-started]
An image does not exist locally with the tag: docker/getting-started

    Why did it fail? The push command was looking for an image named docker/getting-started, but didn't find one. If you run docker image ls, you won't see one either.

    To fix this, you need to tag your existing image you've built to give it another name.

  2. Sign in to Docker Hub using the command docker login -u YOUR-USER-NAME.

  3. Use the docker tag command to give the getting-started image a new name. Replace YOUR-USER-NAME with your Docker ID.

    $ docker tag getting-started YOUR-USER-NAME/getting-started

  4. Now run the docker push command again. If you're copying the value from Docker Hub, you can drop the tagname part, as you didn't add a tag to the image name. If you don't specify a tag, Docker uses a tag called latest.

    $ docker push YOUR-USER-NAME/getting-started

Run the image on a new instance

Now that your image has been built and pushed into a registry, try running your app on a brand new instance that has never seen this container image. To do this, you will use Play with Docker.

Note

Play with Docker uses the amd64 platform. If you are using an ARM based Mac with Apple silicon, you will need to rebuild the image to be compatible with Play with Docker and push the new image to your repository.

To build an image for the amd64 platform, use the --platform flag.

$ docker build --platform linux/amd64 -t YOUR-USER-NAME/getting-started .

Docker buildx also supports building multi-platform images. To learn more, see Multi-platform images.

  1. Open your browser to Play with Docker.

  2. Select Login and then select docker from the drop-down list.

  3. Sign in with your Docker Hub account and then select Start.

  4. Select the ADD NEW INSTANCE option on the left side bar. If you don't see it, make your browser a little wider. After a few seconds, a terminal window opens in your browser.

    Play with Docker add new instance

  5. In the terminal, start your freshly pushed app.

    $ docker run -dp 0.0.0.0:3000:3000 YOUR-USER-NAME/getting-started

    You should see the image get pulled down and eventually start up.

    Tip

    You may have noticed that this command binds the port mapping to a different IP address. Previous docker run commands published ports to 127.0.0.1:3000 on the host. This time, you're using 0.0.0.0.

    Binding to 127.0.0.1 only exposes a container's ports to the loopback interface. Binding to 0.0.0.0, however, exposes the container's port on all interfaces of the host, making it available to the outside world.

    For more information about how port mapping works, see Networking.

  6. Select the 3000 badge when it appears.

    If the 3000 badge doesn't appear, you can select Open Port and specify 3000.

Summary

In this section, you learned how to share your images by pushing them to a registry. You then went to a brand new instance and were able to run the freshly pushed image. This is quite common in CI pipelines, where the pipeline will create the image and push it to a registry and then the production environment can use the latest version of the image.

Related information:

Next steps

In the next section, you'll learn how to persist data in your containerized application.

Persist the DB