why update aks cluster also update the node image

user_9259993 0
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When running below az aks command, it also (unexpectedly) upgrades the node image of all the nodes in all the node pools of this AKS cluster to the latest version...

az aks update \
  --resource-group {resource_group} \
  --subscription {subscription} \
  --name {cluster_name} \
  --load-balancer-outbound-ips {ip_entry}

Cannot find any AKS documentation that mentions why and how this would behave. It's expected that the command above only update the LB outbound IP but the unexpected node image upgrade which took much longer (i.e. one additional hour) to complete just a single and simple operation.

azure-aks azure-devops azure
1 Answers

Update is part of Upgrade.When you upgrade your cluster, the following Kubenetes events may occur on each node:

  • Surge – Create surge node.
  • Drain – Pods are being evicted from the node. Each pod has a 30-minute timeout to complete the eviction.
  • Update – Update of a node has succeeded or failed.
  • Delete – Deleted a surge node.

So when you are using az aks update that do Update a managed Kubernetes cluster,so by default its also updating the node image version to the latest in version including load balancer.

Reference : https://docs.microsoft.com/en-us/azure/aks/upgrade-cluster

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