Which upgrade method can be used for an ‘in-place’ Kubernetes update?

An in-place upgrade of a Tanzu Kubernetes cluster is performed by declaratively changing the desired Kubernetes version in the cluster's object manifest. The kubectl patch command is the standard method used to modify the tanzuKubernetesRelease (TKR) property within the TanzuKubernetesCluster object's specification. Once this change is applied, the Tanzu Supervisor controllers detect the modification and initiate a rolling upgrade of the control plane and worker nodes to the specified TKR version, ensuring a non-disruptive update process.

B. Changing the VirtualMachineClass modifies the CPU and memory resources of the cluster nodes; this is a vertical scaling operation, not a Kubernetes version upgrade.

C. Changing the number of control plane nodes is a horizontal scaling operation to enhance high availability and does not alter the Kubernetes software version.

D. Changing the StorageClass affects the default storage provisioning for new persistent volumes within the cluster, not the Kubernetes version of the cluster itself.

1. VMware vSphere 8.0 Documentation

vSphere with Tanzu Configuration and Management

"Upgrade a Tanzu Kubernetes Cluster". This section explicitly states

"To upgrade a Tanzu Kubernetes cluster

you use kubectl to edit the TanzuKubernetesCluster object manifest. Specifically

you edit the tanzuKubernetesRelease property to reference the new Kubernetes version." It provides the exact kubectl patch command as the method.

2. VMware vSphere 7.0 Documentation

Managing Tanzu Kubernetes Clusters

"Upgrade a Tanzu Kubernetes Cluster by Updating the TKR Version". This document for a prior version confirms the same procedure: "You upgrade a Tanzu Kubernetes cluster by changing the version of the Tanzu Kubernetes release that is specified in the cluster manifest... Use the kubectl patch command to update the TKR version."