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Karpenter for AKS

Requirements​

Before installing the Karpenter, make sure you have the following prerequisites:

  • Install az cli command-line tool.
  • Have an active connection to the desired cluster.
  • Install Helm.

Installation Steps​

Follow these steps to install the Karpenter:

Set the variables the rest of the steps use​

export CLUSTER_NAME=<your-aks-cluster>
export RG=<your-resource-group>
export KARPENTER_NAMESPACE=karpenter
export KARPENTER_IDENTITY=karpentermsi

Read the cluster details​

AKS_JSON=$(az aks show --name "${CLUSTER_NAME}" -g "${RG}")

Create the managed identity for Karpenter​

KMSI_JSON=$(az identity create --name "${KARPENTER_IDENTITY}" --resource-group "${RG}")

Create Karpernter Service Account Auth​

Create federated credential linked to the karpenter service account for auth usage:

az identity federated-credential create --name KARPENTER_FID --identity-name "${KARPENTER_IDENTITY}" --resource-group "${RG}" \
  --issuer "$(jq -r ".oidcIssuerProfile.issuerUrl" <<< "$AKS_JSON")" \
  --subject "system:serviceaccount:${KARPENTER_NAMESPACE}:karpenter-sa" \
  --audience api://AzureADTokenExchange

Create a Role for Karpernter​

Create role assignments to let Karpenter manage VMs and Network resources:

KARPENTER_USER_ASSIGNED_CLIENT_ID=$(jq -r '.principalId' <<< "$KMSI_JSON")
RG_MC=$(jq -r ".nodeResourceGroup" <<< "$AKS_JSON")
RG_MC_RES=$(az group show --name "${RG_MC}" --query "id" -otsv)
for role in "Virtual Machine Contributor" "Network Contributor" "Managed Identity Operator"; do
  az role assignment create --assignee "${KARPENTER_USER_ASSIGNED_CLIENT_ID}" --scope "${RG_MC_RES}" --role "$role"
done

Configure Helm chart values​

Karpeter Helm chart requires some configuration via values to work with a specific AKS cluster. The values are documented in the Helm chart itself, but you can use configure-values.sh to generate karpenter-values.yaml with the required configuration. The script interrogates the AKS cluster and generates the values file, using karpenter-values-template.yaml as a template. (The script fetches the template automatically.)

curl -sO https://raw.githubusercontent.com/Azure/karpenter-provider-azure/main/hack/deploy/configure-values.sh
chmod +x ./configure-values.sh && ./configure-values.sh "${CLUSTER_NAME}" "${RG}" karpenter-sa "${KARPENTER_IDENTITY}" false

Install Karpenter​

export KARPENTER_VERSION=0.5.1   # check the releases page for a newer one

helm upgrade --install karpenter oci://mcr.microsoft.com/aks/karpenter/karpenter \
  --version "${KARPENTER_VERSION}" \
  --namespace "${KARPENTER_NAMESPACE}" --create-namespace \
  --values karpenter-values.yaml \
  --set controller.resources.requests.cpu=1 \
  --set controller.resources.requests.memory=1Gi \
  --set controller.resources.limits.cpu=1 \
  --set controller.resources.limits.memory=1Gi \
  --wait

kubectl logs -f -n "${KARPENTER_NAMESPACE}" -l app.kubernetes.io/name=karpenter -c controller