Changing Engines Mid-Flight: Rolling Kubernetes Upgrades with kubeadm

You will perform the two-minor upgrade in two passes over the cluster, and you
will do it two different ways on purpose:

• Hop 1 (v1.34 → v1.35) — entirely by hand. You will upgrade the
  control-plane nodes, then the worker nodes, running every command yourself so
  you understand exactly what each one does.
• Hop 2 (v1.35 → v1.36) — control plane by hand, workers automated. You will
  supervise the control-plane upgrade as before, then run a provided script that
  performs the identical worker steps across the fleet — demonstrating how the
  same process scales from six nodes to six hundred.

Throughout the worker upgrades you will run a small availability probe against
the CRM and watch the application auto-recover as each node is drained — seeing
first-hand where a rolling upgrade is seamless and where a single-replica tier
briefly blips.

Upon completion of this lab, you will be able to:

• Explain the kubeadm upgrade order and the one-minor-at-a-time rule.
• Point a node's package repository at a target minor version.
• Upgrade the first control-plane node with kubeadm upgrade apply and the
  remaining nodes with kubeadm upgrade node.
• Drain, upgrade, and uncordon nodes safely, one at a time.
• Automate the worker-node upgrade across a fleet with a script.
• Measure how a stateful application recovers during a rolling upgrade.

• 8 x Red Hat Enterprise Linux (RHEL) 9.6 VMs
• Kubernetes 1.34.1