Share the application
Now that we’ve built an image, let’s 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 we’ve used have come from.
A Docker ID allows you to 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 repo
To push an image, we first need to create a repository on Docker Hub.
Click the Create Repository button.
For the repo name, use
getting-started. Make sure the Visibility is
Did you know that Docker offers private repositories which allows you to restrict content to specific users or teams? Check out the details on the Docker pricing page.
Click the Create button!
If you look at the image below an example Docker command can be seen. This command will push to this repo.
Push the image
In the command line, try running the push command you see on Docker Hub. Note that your command will be using your namespace, not “docker”.
$ 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, we need to “tag” our existing image we’ve built to give it another name.
Login to the Docker Hub using the command
docker login -u YOUR-USER-NAME.
docker tagcommand to give the
getting-startedimage a new name. Be sure to swap out
YOUR-USER-NAMEwith your Docker ID.
$ docker tag getting-started YOUR-USER-NAME/getting-started
Learn more about docker tag.
Now try your push command again. If you’re copying the value from Docker Hub, you can drop the
tagnameportion, as we didn’t add a tag to the image name. If you don’t specify a tag, Docker will use a tag called
$ docker push YOUR-USER-NAME/getting-started
Run the image on a new instance
Now that our image has been built and pushed into a registry, let’s try running our app on a brand new instance that has never seen this container image! To do this, we will use Play with Docker.
Open your browser to Play with Docker.
Click Login and then select docker from the drop-down list.
Connect with your Docker Hub account.
Once you’re logged in, click on 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.
In the terminal, start your freshly pushed app.
$ docker run -dp 3000:3000 YOUR-USER-NAME/getting-started
You should see the image get pulled down and eventually start up!
Click on the 3000 badge when it comes up and you should see the app with your modifications! Hooray! If the 3000 badge doesn’t show up, you can click on the “Open Port” button and type in 3000.
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.
Now you can circle back around to what you noticed at the end of the last section. As a reminder, you noticed that when you restarted the app, you lost all of your todo list items. That’s obviously not a great user experience, so next you’ll learn how you can persist the data across restarts!