kubernetes cluster autoscaler

Prerequisites

Before deploying, you need:

1. An AWS account with an Auto Scaling Group configured
2. An IAM user with permissions to describe and manage Auto Scaling Groups
3. AWS access credentials (Access Key ID and Secret Access Key) for the IAM user
4. The name of your Auto Scaling Group and the AWS region it's in

Step 1: Add the Helm Repository

helm repo add autoscaler https://kubernetes.github.io/autoscaler
helm repo update

Step 2: Create a values.yaml File

Create a file with your Cluster Autoscaler configuration. Replace the placeholder values with your actual AWS configuration:

image:
  repository: <your-namespace>/dhi-kubernetes-cluster-autoscaler
  tag: <tag>
  pullPolicy: IfNotPresent
  # pullSecrets:  # Uncomment only if using a private registry
  #   - <secret-name>

autoscalingGroups:
  - name: my-test-asg
    minSize: 0
    maxSize: 3

cloudProvider: aws
awsRegion: us-east-1

# AWS Credentials (use your actual valid credentials with ASG permissions)
awsAccessKeyID: "YOUR_AWS_ACCESS_KEY_ID"
awsSecretAccessKey: "YOUR_AWS_SECRET_ACCESS_KEY"

rbac:
  create: true
  serviceAccount:
    create: true
    name: cluster-autoscaler

Required replacements:

• my-test-asg: Replace with your actual Auto Scaling Group name in AWS
• us-east-1: Replace with the AWS region where your ASG is located
• YOUR_AWS_ACCESS_KEY_ID: Replace with your AWS IAM user's access key ID
• YOUR_AWS_SECRET_ACCESS_KEY: Replace with your AWS IAM user's secret access key

Optional replacements:

• pullSecrets: Only needed if you're using a private container registry. Uncomment and set the secret name if required.

Step 3: Deploy the Helm Chart

helm install cluster-autoscaler autoscaler/cluster-autoscaler \
  --namespace kube-system \
  --values values.yaml

Step 4: Verify the Deployment

Check if the pod is running:

kubectl get pods -n kube-system -l "app.kubernetes.io/name=aws-cluster-autoscaler"

You should see a pod in Running status. Check the logs to confirm it's connecting to AWS:

kubectl logs -n kube-system -l "app.kubernetes.io/name=aws-cluster-autoscaler"

You should see messages indicating successful AWS API calls and Auto Scaling Group discovery.

Production Recommendations

For production environments, consider using IAM Roles for Service Accounts (IRSA) instead of static credentials. IRSA allows your Kubernetes pods to authenticate to AWS without storing credentials in your cluster. Refer to the official Helm chart documentation for IRSA configuration options.

Image variants

Ghost hardened images come in different variants depending on their intended use. Image variants are identified by their tag.

• Runtime variants are designed to run your application in production. These images are intended to be used either directly or as the FROM image in the final stage of a multi-stage build. These images typically:

  • Run as a nonroot user
  • Do not include a shell or a package manager
  • Contain only the minimal set of libraries needed to run the app

• Build-time variants typically include dev in the tag name and are intended for use in the first stage of a multi-stage Dockerfile. These images typically:

  • Run as the root user
  • Include a shell and package manager
  • Are used to build or compile applications

• FIPS variants include fips in the variant name and tag. They come in both runtime and build-time variants. These variants use cryptographic modules that have been validated under FIPS 140, a U.S. government standard for secure cryptographic operations. For example, usage of MD5 fails in FIPS variants.

To view the image variants and get more information about them, select the Tags tab for this repository, and then select a tag.

Migrate to a Ghost hardened image

To migrate your application to a Ghost hardened image, you must update your Dockerfile. At minimum, you must update the base image in your existing Dockerfile to a Ghost hardened image. This and a few other common changes are listed in the following table of migration notes.

The following steps outline the general migration process.

1. Find hardened images for your app.

   A hardened image may have several variants. Inspect the image tags and find the image variant that meets your needs.

2. Update the base image in your Dockerfile.

   Update the base image in your application's Dockerfile to the hardened image you found in the previous step. For framework images, this is typically going to be an image tagged as dev because it has the tools needed to install packages and dependencies.

3. For multi-stage Dockerfiles, update the runtime image in your Dockerfile.

   To ensure that your final image is as minimal as possible, you should use a multi-stage build. All stages in your Dockerfile should use a hardened image. While intermediary stages will typically use images tagged as dev, your final runtime stage should use a non-dev image variant.

4. Install additional packages

   Ghost hardened images contain minimal packages in order to reduce the potential attack surface. You may need to install additional packages in your Dockerfile. To view if a package manager is available for an image variant, select the Tags tab for this repository. To view what packages are already installed in an image variant, select the Tags tab for this repository, and then select a tag.

   Only images tagged as dev typically have package managers. You should use a multi-stage Dockerfile to install the packages. Install the packages in the build stage that uses a dev image. Then, if needed, copy any necessary artifacts to the runtime stage that uses a non-dev image.

   For Alpine-based images, you can use apk to install packages. For Debian-based images, you can use apt-get to install packages.

Troubleshooting migration

The following are common issues that you may encounter during migration.

General debugging

The hardened images intended for runtime don't contain a shell nor any tools for debugging. The recommended method for debugging applications built with Ghost hardened images is to use Docker Debug to attach to these containers. Docker Debug provides a shell, common debugging tools, and lets you install other tools in an ephemeral, writable layer that only exists during the debugging session.

Permissions

By default image variants intended for runtime, run as a nonroot user. Ensure that necessary files and directories are accessible to that user. You may need to copy files to different directories or change permissions so your application running as a nonroot user can access them.

To view the user for an image variant, select the Tags tab for this repository.

Privileged ports

Non-dev hardened images run as a nonroot user by default. As a result, applications in these images can't bind to privileged ports (below 1024) when running in Kubernetes or in Docker Engine versions older than 20.10. To avoid issues, configure your application to listen on port 1025 or higher inside the container, even if you map it to a lower port on the host. For example, docker run -p 80:8080 my-image will work because the port inside the container is 8080, and docker run -p 80:81 my-image won't work because the port inside the container is 81.

No shell

By default, image variants intended for runtime don't contain a shell. Use dev images in build stages to run shell commands and then copy any necessary artifacts into the runtime stage. In addition, use Docker Debug to debug containers with no shell.

To see if a shell is available in an image variant and which one, select the Tags tab for this repository.

Entry point

Ghost hardened images may have different entry points than images such as Docker Official Images.

To view the Entrypoint or CMD defined for an image variant, select the Tags tab for this repository, select a tag, and then select the Specifications tab.