How to Manage Kubernetes Images

This post will cover topic related to ‘How to Manage Kubernetes Images’ with multiple docker command examples and different scenerios. So this will help you to understand the command docker and options available in it. Also this post will explain you how to use docker command.

Docker is a powerful tool used for containerization, allowing developers to package applications and their dependencies into lightweight, portable containers. Managing Kubernetes images is crucial for deploying applications in Kubernetes clusters efficiently. The Docker image command plays a central role in handling these images.

1. List all Docker images:
To view all images stored locally, use the command:

docker image ls

This command lists all Docker images along with details such as repository, tag, and image ID.
Example Output:

        REPOSITORY          TAG       IMAGE ID       CREATED       SIZE
        nginx               latest    abcdef123456   2 weeks ago   132MB
        postgres            12        xyz987654321   3 weeks ago   356MB
        

To verify, run the command and check if it displays a list of images with their details.

2. Pull a Docker image:
To download a Docker image from a registry (like Docker Hub), use:

docker image pull nginx

This command fetches the latest nginx image from Docker Hub.
Example Output:

        latest: Pulling from library/nginx
        Digest: sha256:abcdef123456...
        Status: Downloaded newer image for nginx:latest
        

Verify by checking if the image is downloaded successfully and displayed in the list from the previous command.

3. Remove a Docker image:
To delete an image from the local repository, use:

docker image rm nginx

This command removes the nginx image from the local Docker repository.
Example Output:

        Untagged: nginx:latest
        Untagged: nginx@sha256:abcdef123456...
        Deleted: sha256:xyz987654321...
        

Verify by re-running the docker image ls command and confirming that the image is no longer listed.

4. Tag a Docker image:
To add a tag to an existing image, use:

docker image tag nginx mynginx:1.0

This creates a new tag mynginx:1.0 for the nginx image.
Example Output:
No specific output is generated, but verify by listing images (docker image ls) to see the new tag associated with the image.

5. Inspect a Docker image:
To get detailed information about an image, including its layers and metadata, use:

docker image inspect nginx

This command provides a JSON object containing all the information about the nginx image.
Example Output:

        [
          {
            "Id": "sha256:abcdef123456...",
            "RepoTags": [
              "nginx:latest"
            ],
            "Container": "1234abcd...",
            ...
          }
        ]
        

Verify by checking if detailed information about the image is displayed.

6. Build a Docker image:
To create a new Docker image using a Dockerfile and context, use:

docker image build -t myapp .

This command builds an image named myapp using the Dockerfile in the current directory (.).
Example Output:
Depending on the Dockerfile, the output will show each step of the build process. Verify by checking if the build completes successfully and the image is listed using docker image ls.

7. Push a Docker image:
To upload a Docker image to a registry (like Docker Hub), use:

docker image push myapp

This command pushes the myapp image to the default repository (e.g., Docker Hub).
Example Output:
Depending on the size of the image, it will display progress and confirmation messages. Verify by checking if the image appears in the registry (e.g., Docker Hub).

8. Save a Docker image:
To save an image as a tar archive file, use:

docker image save -o nginx.tar nginx

This command saves the nginx image as nginx.tar in the current directory.
Example Output:
No specific output on success, but verify by checking if nginx.tar file is created in the current directory.

9. Load a Docker image:
To load an image from a tar archive file, use:

docker image load -i nginx.tar

This command loads the nginx.tar file as a Docker image.
Example Output:
Displays progress as the image is loaded. Verify by listing images (docker image ls) to see if nginx image is added.

10. Prune unused Docker images:
To remove all unused images (not referenced by any container), use:

docker image prune

This command cleans up disk space by removing unused images.
Example Output:

        Deleted Images:
        untagged: nginx@sha256:abcdef123456...
        deleted: sha256:xyz987654321...
        

Verify by checking if the command outputs a list of deleted images and confirms the reclaimed space.

Also check similar articles.

How to Manage Kubernetes Contexts
How to Manage Kubernetes Containers
How to Manage Kubernetes Container Checkpoints
How to Manage Kubernetes Build Processes
Search Kubernetes for Docker Images