91 lines
3.5 KiB
Markdown
91 lines
3.5 KiB
Markdown
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Now that we've built an image, let's share it! To share Docker images, you have to use a Docker
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registry. The default registry is Docker Hub and is where all of the images we've used have come from.
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## Create a Repo
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To push an image, we first need to create a repo on Docker Hub.
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1. Go to [Docker Hub](https://hub.docker.com) and log in if you need to.
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1. Click the **Create Repository** button.
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1. For the repo name, use `getting-started`. Make sure the Visibility is `Public`.
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1. Click the **Create** button!
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If you look on the right-side of the page, you'll see a section named **Docker commands**. This gives
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an example command that you will need to run to push to this repo.
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{: style=width:75% }
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{: .text-center }
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## Pushing our Image
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1. In the command line, try running the push command you see on Docker Hub. Note that your command
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will be using your namespace, not "docker".
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```plaintext
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$ docker push docker/getting-started
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The push refers to repository [docker.io/docker/getting-started]
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An image does not exist locally with the tag: docker/getting-started
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```
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Why did it fail? The push command was looking for an image named docker/getting-started, but
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didn't find one. If you run `docker image ls`, you won't see one either.
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To fix this, we need to "tag" our existing image we've built to give it another name.
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1. Login to the Docker Hub using the command `docker login -u YOUR-USER-NAME`.
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1. Use the `docker tag` command to give the `getting-started` image a new name. Be sure to swap out
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`YOUR-USER-NAME` with your Docker ID.
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```bash
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docker tag getting-started YOUR-USER-NAME/getting-started
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```
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1. Now try your push command again. If you're copying the value from Docker Hub, you can drop the
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`tagname` portion, as we didn't add a tag to the image name. If you don't specify a tag, Docker
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will use a tag called `latest`.
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```bash
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docker push YOUR-USER-NAME/getting-started
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```
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## Running our Image on a New Instance
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Now that our image has been built and pushed into a registry, let's try running our app on a brand
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new instance that has never seen this container image! To do this, we will use Play with Docker.
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1. Open your browser to [Play with Docker](http://play-with-docker.com).
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1. Log in with your Docker Hub account.
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1. Once you're logged in, click on the "+ ADD NEW INSTANCE" link in the left side bar. After a few
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seconds, a terminal window will be opened in your browser.
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1. In the terminal, start your freshly pushed app.
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```bash
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docker run -dp 3000:3000 YOUR-USER-NAME/getting-started
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```
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You should see the image get pulled down and eventually start up!
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1. Click on the 3000 badge when it comes up and you should see the app with your modifications! Hooray!
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If the 3000 badge doesn't show up, you can click on the "Open Port" button and type in 3000.
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## Recap
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In this section, we learned how to share our images by pushing them to a registry. We then went to a
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brand new instance and were able to run the freshly pushed image. This is quite common in CI pipelines,
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where the pipeline will create the image and push it to a registry and then the production environment
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can use the latest version of the image.
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Now that we have that figured out, let's circle back around to what we noticed at the end of the last
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section. As a reminder, we noticed that when we restarted the app, we lost all of our todo list items.
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That's obviously not a great user experience, so let's learn how we can persist the data across
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restarts!
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