step4.md

4. Create a Docker container image

Estimated time: 50 min remaining

Next, create a Dockerfile which describes the image that you want to build. Docker container images can extend from other existing images so for this image, we'll extend from an existing Node image.

$ nano Dockerfile
FROM node:0.12
EXPOSE 8080
COPY server.js .
CMD node server.js

This “recipe” for the Docker image will start from the node image found on the Docker hub, expose port 8080, copy our server.js file to the image and start the node server as we previously did manually.

Save this Dockerfile and build this image by running:

$ docker build -t gcr.io/PROJECT_ID/hello-node:v1 .

Once this completes (it’ll take some time to download and extract everything) you can test the image locally with the following command which will run a Docker container as a daemon on port 8080 from our newly-created container image:

$ docker run -d -p 8080:8080 gcr.io/PROJECT_ID/hello-node:v1
325301e6b2bffd1d0049c621866831316d653c0b25a496d04ce0ec6854cb7998

And again take advantage of the Web preview feature of CloudShell:

Or use ‘curl’ or ‘wget’ from your CloudShell prompt if you’d like:

$ curl http://localhost:8080
Hello World!

Note: Here’s the full documentation for the docker run command.

Let’s now stop the container:

$ docker ps
CONTAINER ID        IMAGE                              COMMAND
2c66d0efcbd4        gcr.io/PROJECT_ID/hello-node:v1    "/bin/sh -c 'node    
$ docker stop 2c66d0efcbd4
2c66d0efcbd4

Now that the image works as intended we can push it to the Google Container Registry, a private repository for your Docker images accessible from every Google Cloud project (but also from outside Google Cloud Platform):

$ gcloud docker push gcr.io/PROJECT_ID/hello-node:v1

If all goes well, you should be able to see the container image listed in the console: Compute > Container Engine > Container Registry. We now have a project-wide Docker image available which Kubernetes can access and orchestrate as we’ll see in a few minutes.

Note: While here we used a generic domain for the registry (gcr.io), you can also be more specific about which zone and bucket to use, details are documented here.

If you’re curious, you can navigate through the container images as they are stored in Google Cloud Storage by following this link.

Note: The full link should read https://console.cloud.google.com/storage/browser?project=PROJECT_ID

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