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ms.custom: sap:Create, Upgrade, Scale and Delete operations (cluster or nodepool)
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- AKS node pool names must be all lowercase. The names must be 1-12 characters in length for Linux node pools and 1-6 characters for Windows node pools. A name must start with a letter, and the only allowed characters are letters and numbers.
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- The *admin-username*, which sets the administrator user name for Linux nodes, must start with a letter. This user name may only contain letters, numbers, hyphens, and underscores. It has a maximum length of 32 characters.
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- The *aksmanagedap* is blocked as a reserved name for AKS system components. It can't be used for nodepools.
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For more information about naming convention. see the following resources:
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- [Naming rules and restrictions for Azure resources](/azure/azure-resource-manager/management/resource-name-rules#microsoftcontainerservice)
Copy file name to clipboardExpand all lines: support/azure/azure-kubernetes/create-upgrade-delete/cannot-scale-cluster-autoscaler-enabled-node-pool.md
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@@ -3,14 +3,14 @@ title: Cluster autoscaler fails to scale with cannot scale cluster autoscaler en
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description: Learn how to troubleshoot the cannot scale cluster autoscaler enabled node pool error when your autoscaler isn't scaling up or down.
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author: sgeannina
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ms.author: ninasegares
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ms.date: 10/17/2023
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ms.reviewer: aritraghosh, chiragpa
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ms.date: 04/17/2025
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ms.reviewer: aritraghosh, chiragpa.momajed
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ms.service: azure-kubernetes-service
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ms.custom: sap:Create, Upgrade, Scale and Delete operations (cluster or nodepool)
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---
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# Cluster autoscaler fails to scale with "cannot scale cluster autoscaler enabled node pool" error
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This article discusses how to resolve the "cannot scale cluster autoscaler enabled node pool" error that appears when scaling a cluster with an autoscalerenabled node pool.
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This article discusses how to resolve the "cannot scale cluster autoscaler enabled node pool" error that occurs when you scale a cluster that has an autoscaler-enabled node pool.
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## Symptoms
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## Troubleshooting checklist
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Azure Kubernetes Service (AKS) uses virtual machine scale sets-based agent pools, which contain cluster nodes and [cluster autoscaling capabilities](/azure/aks/cluster-autoscaler) if enabled.
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Azure Kubernetes Service (AKS) uses Azure Virtual Machine Scale Sets-based agent pools. These pools contain cluster nodes and [cluster autoscaling capabilities](/azure/aks/cluster-autoscaler), if they're enabled.
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### Check that the cluster virtual machine scale set exists
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1. Sign in to [Azure portal](https://portal.azure.com).
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1. Find the node resource group by searching the following names:
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- The default name `MC_{AksResourceGroupName}_{YourAksClusterName}_{AksResourceLocation}`.
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- The custom name (if it was provided at creation).
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1. Sign in to the [Azure portal](https://portal.azure.com).
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1. Find the node resource group by searching for the following names:
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- The default name `MC_{AksResourceGroupName}_{YourAksClusterName}_{AksResourceLocation}`
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- The custom name (if it was provided at creation)
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>
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> [!NOTE]
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> When you create a new cluster, AKS automatically creates a second resource group to store the AKS resources. For more information, see [Why are two resource groups created with AKS?](/azure/aks/faq#why-are-two-resource-groups-created-with-aks)
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> When you create a cluster, AKS automatically creates a second resource group to store the AKS resources. For more information, see [Why are two resource groups created with AKS?](/azure/aks/faq#why-are-two-resource-groups-created-with-aks)
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1. Check the list of resources and make sure that there's a virtual machine scale set.
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1. Check the list of resources to make sure that a virtual machine scale set exists.
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## Cause 1: The cluster virtual machine scale set was deleted
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Deleting the virtual machine scale set attached to the clustercauses the cluster autoscaler to fail. It also causes issues when provisioning resources such as nodes and pods.
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If you delete the virtual machine scale set that's attached to the cluster, this action causes the cluster autoscaler to fail. It also causes issues when you provision resources such as nodes and pods.
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> [!NOTE]
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> Modifying any resource under the node resource group in the AKS cluster is an unsupported action and will cause cluster operation failures. You can prevent changes from being made to the node resource group by [blocking users from modifying resources](/azure/aks/cluster-configuration#fully-managed-resource-group-preview) managed by the AKS cluster.
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> Modifying any resource under the node resource group in the AKS cluster is an unsupported action and causes cluster operation failures. You can prevent changes from being made to the node resource group by [blocking users from modifying resources](/azure/aks/cluster-configuration#fully-managed-resource-group-preview) that are managed by the AKS cluster.
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### Reconcile node pool
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If the cluster virtual machine scale set is accidentally deleted, you can reconcile the node pool by using `az aks nodepool update`:
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```bash
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# Update Node Pool Configuration
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az aks nodepool update --resource-group <resource-group-name> --cluster-name <cluster-name> --name <nodepool-name> --tags <tags> --node-taints <taints> --labels <labels>
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# Verify the Update
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az aks nodepool show --resource-group <resource-group-name> --cluster-name <cluster-name> --name <nodepool-name>
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```
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Monitor the node pool to make sure that it's functioning as expected and that all nodes are operational.
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## Cause 2: Tags or any other properties were modified from the node resource group
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You may receive scaling errors if you modify or delete Azure-created tags and other resource properties in the node resource group. For more information, see [Can I modify tags and other properties of the AKS resources in the node resource group?](/azure/aks/faq#can-i-modify-tags-and-other-properties-of-the-aks-resources-in-the-node-resource-group)
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You may experience scaling errors if you modify or delete Azure-created tags and other resource properties in the node resource group. For more information, see [Can I modify tags and other properties of the AKS resources in the node resource group?](/azure/aks/faq#can-i-modify-tags-and-other-properties-of-the-aks-resources-in-the-node-resource-group)
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### Reconcile node resource group tags
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Use the Azure CLI to make sure that the node resource group has the correct tags for AKS name and the AKS group name:
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```bash
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# Add or update tags for AKS name and AKS group name
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az group update --name <node-resource-group-name> --set tags.AKS-Managed-Cluster-Name=<aks-managed-cluster-name> tags.AKS-Managed-Cluster-RG=<aks-managed-cluster-rg>
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# Verify the tags
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az group show --name <node-resource-group-name> --query "tags"
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```
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Monitor the resource group to make sure that the tags are correctly applied and that the resource group is functioning as expected.
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## Cause 3: The cluster node resource group was deleted
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Deleting the cluster node resource group causes issues when provisioning the infrastructure resources required by the cluster, which causes the cluster autoscaler to fail.
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Deleting the cluster node resource group causes issues when you provision the infrastructure resources that are required by the cluster. This action causes the cluster autoscaler to fail.
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## Solution: Update the cluster to the goal state without changing the configuration
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To resolve this issue, you can run the following command to recover the deleted virtual machine scale set or any tags (missing or modified):
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To resolve this issue, run the following command to recover the deleted virtual machine scale set or any tags (missing or modified).
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> [!NOTE]
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> It might take a few minutes until the operation completes.
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> It might take a few minutes until the operation finishes.
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```azurecli
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az aks update --resource-group <resource-group-name> --name <aks-cluster-name>
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```
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### Additional troubleshooting tips
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- Check the Azure Activity Log for any recent changes or deletions.
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[!INCLUDE [Azure Help Support](../../../includes/azure-help-support.md)]
description: Learn how to resolve Container Network Interface download failures when you try to create and deploy an Azure Kubernetes Service (AKS) cluster.
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