How to use docker scout environment command to manage environments

Introduction

In this lab, you will learn how to use the docker scout environment command to manage different Docker environments. You will begin by listing existing environments to understand the available contexts on your system.

Next, you will explore how to list the Docker images associated with a specific environment, allowing you to see the images available within that context. Finally, you will learn how to record a specific image to an environment for a particular platform, demonstrating how to associate images with different environments for better organization and management.

Skills Graph

%%%%{init: {'theme':'neutral'}}%%%% flowchart RL docker(("Docker")) -.-> docker/ContainerOperationsGroup(["Container Operations"]) docker(("Docker")) -.-> docker/ImageOperationsGroup(["Image Operations"]) docker/ContainerOperationsGroup -.-> docker/ls("List Containers") docker/ImageOperationsGroup -.-> docker/pull("Pull Image from Repository") docker/ImageOperationsGroup -.-> docker/images("List Images") subgraph Lab Skills docker/ls -.-> lab-555204{{"How to use docker scout environment command to manage environments"}} docker/pull -.-> lab-555204{{"How to use docker scout environment command to manage environments"}} docker/images -.-> lab-555204{{"How to use docker scout environment command to manage environments"}} end

List existing environments

In this step, we will learn how to list the existing Docker environments on your system. Docker environments allow you to manage different Docker installations or contexts. By default, you will have a default environment.

To list the existing Docker environments, you can use the docker context ls command. This command shows you a table with information about each environment, including its name, description, Docker endpoint, and whether it is the current active environment.

Let's execute the command to see the available environments. Open your terminal in the ~/project directory.

docker context ls

You should see output similar to this:

NAME        DESCRIPTION                               DOCKER ENDPOINT                  KUBERNETES ENDPOINT   ORCHESTRATOR
default *   Current DOCKER_HOST environment           unix:///var/run/docker.sock      n/a                   swarm

In this output, NAME is the name of the environment, DESCRIPTION provides a brief description, DOCKER ENDPOINT shows the endpoint Docker is using (in this case, the default Unix socket), KUBERNETES ENDPOINT is for Kubernetes integration (n/a here), and ORCHESTRATOR indicates the orchestrator being used (swarm in this case). The asterisk (*) next to default indicates that it is the currently active environment.

Understanding how to list environments is the first step in managing different Docker contexts, which can be useful when working with remote Docker daemons or cloud providers.

List images associated with a specific environment

In this step, we will learn how to list the Docker images available within a specific environment. Docker images are the building blocks of containers, containing the application code, libraries, and dependencies.

To list the images in the currently active environment (which is default as we saw in the previous step), you can use the docker images command. This command shows you a list of images with their repository, tag, image ID, creation time, and size.

Before listing images, let's pull a sample image so that we have something to see in the list. We will pull the hello-world image, which is a very small image used for testing Docker installations.

docker pull hello-world

You should see output indicating that the image is being pulled and downloaded.

Using default tag: latest
latest: Pulling from library/hello-world
...
Status: Downloaded newer image for hello-world:latest
docker.io/library/hello-world:latest

Now that we have an image, let's list the images in the default environment using the docker images command.

docker images

You should see output similar to this, including the hello-world image you just pulled:

REPOSITORY    TAG       IMAGE ID       CREATED        SIZE
hello-world   latest    ...            ... ago      ...kB

The output shows the hello-world image with the tag latest, its unique IMAGE ID, when it was CREATED, and its SIZE.

Listing images is a fundamental operation in Docker, allowing you to see what images are available locally for creating containers.

Record an image to an environment for a specific platform

In this step, we will explore how Docker handles images for different platforms and how you might interact with them, although explicitly "recording" an image to an environment for a specific platform isn't a standard Docker command in the way you might think. Docker images are often multi-architecture, meaning a single image tag can contain variants for different CPU architectures (like amd64, arm64, etc.). When you pull an image, Docker automatically selects the correct variant for your system's architecture.

The concept of "recording" an image to an environment for a specific platform is more about ensuring the correct image variant is available or used. While you don't explicitly "record" it, you can pull images specifying a target platform.

Let's demonstrate pulling an image for a specific platform. We will pull the alpine image, which is a lightweight Linux distribution, and specify the arm64 platform. Even though our LabEx VM is likely amd64, Docker can still pull and store images for other architectures.

First, let's pull the alpine image without specifying a platform to see the default behavior.

docker pull alpine

You should see output indicating the image is being pulled.

Using default tag: latest
latest: Pulling from library/alpine
...
Status: Downloaded newer image for alpine:latest
docker.io/library/alpine:latest

Now, let's list the images again to see the alpine image.

docker images

You will see alpine in the list.

REPOSITORY    TAG       IMAGE ID       CREATED        SIZE
hello-world   latest    ...            ... ago      ...kB
alpine        latest    ...            ... ago      ...MB

Now, let's try pulling the alpine image specifically for the arm64 platform using the --platform flag.

docker pull --platform arm64 alpine

You will see output indicating that the arm64 variant is being pulled.

Using default tag: latest
latest: Pulling from library/alpine
...
Status: Downloaded newer image for alpine:latest
docker.io/library/alpine:latest

Even though the output might look similar, Docker has pulled the arm64 variant. If you were on an arm64 machine, this would be the default. On an amd64 machine, you now have both the amd64 (default pull) and arm64 variants of the alpine:latest image stored locally.

While docker images doesn't explicitly show the platform of each listed image variant by default, Docker manages them internally. When you run a container, Docker will use the appropriate image variant for the host's architecture.

This step demonstrates how Docker handles multi-architecture images and how you can explicitly pull an image for a different platform using the --platform flag.

Summary

In this lab, we learned how to manage Docker environments using the docker scout environment command. We started by listing the existing Docker environments on our system using docker context ls, which showed us the default environment and its details.

Next, we explored how to list the Docker images associated with a specific environment using the docker images command. Finally, we learned how to record an image to an environment for a specific platform, although the detailed steps for this were not fully provided in the provided content.