Docker is an open platform for developing, shipping, and running applications. With Docker, you can separate your applications from your infrastructure and treat your infrastructure like a managed application. Docker helps you ship code faster, test faster, deploy faster, and shorten the cycle between writing code and running code.

Docker does this by combining kernel containerization features with workflows and tooling that helps you manage and deploy your applications.

Docker containers can be directly used in Kubernetes, which allows them to be run in the Kubernetes Engine with ease. After learning the essentials of Docker, you will have the skillset to start developing Kubernetes and containerized applications.

What you'll learn

In this lab, you will learn how to do the following:

• How to build, run, and debug Docker containers.
• How to pull Docker images from Docker Hub and Google Container Registry.
• How to push Docker images to Google Container Registry.

Hello World

Open up Cloud Shell and enter the following command to run a hello world container to get started:

docker run hello-world

(Command Output)

Unable to find image 'hello-world:latest' locally
latest: Pulling from library/hello-world
9db2ca6ccae0: Pull complete
Digest: sha256:4b8ff392a12ed9ea17784bd3c9a8b1fa3299cac44aca35a85c90c5e3c7afacdc
Status: Downloaded newer image for hello-world:latest

Hello from Docker!
This message shows that your installation appears to be working correctly.
...

This simple container returns Hello from Docker! to your screen. While the command is simple, notice in the output the number of steps it performed. The docker daemon searched for the hello-world image, didn't find the image locally, pulled the image from a public registry called Docker Hub, created a container from that image, and ran the container for you.

Run the following command to take a look at the container image it pulled from Docker Hub:

docker images

(Command Output)

REPOSITORY     TAG      IMAGE ID       CREATED       SIZE
hello-world    latest   1815c82652c0   6 days ago    1.84 kB

This is the image pulled from the Docker Hub public registry. The Image ID is in SHA256 hash format—this field specifies the Docker image that's been provisioned. When the docker daemon can't find an image locally, it will by default search the public registry for the image. Let's run the container again: