Kubernetes Cluster Upgrade Using kubeadm (v1.35.1 → v1.35.2) | Complete Step-by-Step Guide

July 23, 2026 by [email protected]

A Kubernetes cluster consists of two main components:

• Control Plane (Master Node): Manages the cluster and makes scheduling decisions.
• Worker Nodes: Run the application workloads (Pods).

The recommended upgrade order is:

1. Upgrade the Control Plane.
2. Upgrade each Worker Node, one at a time.
3. Verify the health of the cluster after each upgrade.

In this tutorial, we will upgrade a Kubernetes cluster from v1.35.1 to v1.35.2 using kubeadm.

Kubernetes Cluster Architecture

                    Kubernetes Cluster
    ---------------------------------------------------

           +-----------------------------------+
           |          Control Plane            |
           |           v1.35.1                 |
           +----------------+------------------+
                            |
          ------------------------------------------
          |                                        |
+----------------------+               +----------------------+
|    Worker Node 01    |               |    Worker Node 02    |
|       v1.35.1        |               |       v1.35.1        |
+----------------------+               +----------------------+

        Upgrade Order

1. Control Plane
        ↓
2. Worker Node 01
        ↓
3. Worker Node 02

Prerequisites

Before starting the upgrade, ensure that:

• Kubernetes cluster is healthy.
• All nodes are in the Ready state.
• You have root or sudo privileges.
• Internet access is available.
• A backup of etcd has been taken (recommended for production).

Current Cluster Version

kubectl get nodes

Example Output

NAME           STATUS   ROLES           VERSION
controlplane   Ready    control-plane   v1.35.1
node01         Ready    <none>          v1.35.1

Part 1 — Upgrading the Control Plane

The Control Plane manages the Kubernetes cluster. It is responsible for scheduling Pods, maintaining cluster state, handling API requests, and coordinating all cluster operations.

Always upgrade the Control Plane first.

Step 1 — Check the Current kubeadm Version

kubeadm version

Step 2 — Check Available Upgrade Versions

sudo kubeadm upgrade plan

This command displays:

• Current cluster version
• Available upgrade versions
• Components that require upgrading

Step 3 — Upgrade kubeadm

Remove the package hold.

sudo apt-mark unhold kubeadm

Update package information.

sudo apt update

Install the latest kubeadm package.

sudo apt install -y kubeadm='1.35.2-1.1'

Lock the package again.

sudo apt-mark hold kubeadm

Verify the version.

kubeadm version

Step 4 — Upgrade the Control Plane

Verify the upgrade plan again.

sudo kubeadm upgrade plan

Apply the upgrade.

sudo kubeadm upgrade apply v1.35.2

Type y when prompted.

Successful Output

SUCCESS!

Your Kubernetes control plane has been upgraded.

Step 5 — Upgrade kubelet and kubectl

sudo apt-mark unhold kubelet kubectl

sudo apt install -y kubelet='1.35.2-1.1' kubectl='1.35.2-1.1'

sudo apt-mark hold kubelet kubectl

Restart kubelet.

sudo systemctl daemon-reload

sudo systemctl restart kubelet

Verify.

kubectl version --short

kubectl get nodes

Output

NAME           STATUS   ROLES           VERSION
controlplane   Ready    control-plane   v1.35.2
node01         Ready    <none>          v1.35.1

The Control Plane upgrade is now complete.

Part 2 — Upgrading the Worker Node

Now upgrade each worker node individually.

Step 1 — Drain the Worker Node

Before upgrading, move workloads to other nodes.

kubectl drain node01 --ignore-daemonsets

Verify

kubectl get nodes

Output

node01 Ready,SchedulingDisabled

Step 2 — Login to the Worker Node

ssh node01

Step 3 — Upgrade kubeadm

sudo apt-mark unhold kubeadm

sudo apt update

sudo apt install -y kubeadm='1.35.2-1.1'

sudo apt-mark hold kubeadm

Verify

kubeadm version

Step 4 — Upgrade Node Configuration

sudo kubeadm upgrade node

Successful Output

SUCCESS!

The configuration for this node was successfully upgraded.

Step 5 — Upgrade kubelet and kubectl

sudo apt-mark unhold kubelet kubectl

sudo apt install -y kubelet='1.35.2-1.1' kubectl='1.35.2-1.1'

sudo apt-mark hold kubelet kubectl

Restart kubelet.

sudo systemctl daemon-reload

sudo systemctl restart kubelet

Verify

kubelet --version

Step 6 — Return to the Control Plane

exit

Step 7 — Enable Scheduling Again

kubectl uncordon node01

Step 8 — Verify the Cluster

kubectl get nodes

Expected Output

NAME           STATUS   ROLES           VERSION
controlplane   Ready    control-plane   v1.35.2
node01         Ready    <none>          v1.35.2

Congratulations! Your Worker Node has been successfully upgraded.

Complete Upgrade Workflow

                     Start
                       │
                       ▼
          Check Cluster Version
                       │
                       ▼
       Upgrade Control Plane First
                       │
      ┌────────────────┴────────────────┐
      │                                 │
      ▼                                 ▼
Upgrade kubeadm               kubeadm upgrade apply
      │                                 │
      └────────────────┬────────────────┘
                       ▼
         Upgrade kubelet & kubectl
                       │
                       ▼
          Restart kubelet Service
                       │
                       ▼
       Verify Control Plane Version
                       │
                       ▼
        Drain Worker Node (node01)
                       │
                       ▼
          SSH into Worker Node
                       │
                       ▼
            Upgrade kubeadm
                       │
                       ▼
          kubeadm upgrade node
                       │
                       ▼
       Upgrade kubelet & kubectl
                       │
                       ▼
          Restart kubelet Service
                       │
                       ▼
            Exit Worker Node
                       │
                       ▼
          Uncordon Worker Node
                       │
                       ▼
         Verify Cluster Health
                       │
                       ▼
              Upgrade Complete

Complete Command Cheat Sheet

Control Plane

kubectl get nodes

kubeadm version

sudo kubeadm upgrade plan

sudo apt-mark unhold kubeadm
sudo apt update
sudo apt install -y kubeadm='1.35.2-1.1'
sudo apt-mark hold kubeadm

sudo kubeadm upgrade apply v1.35.2

sudo apt-mark unhold kubelet kubectl
sudo apt install -y kubelet='1.35.2-1.1' kubectl='1.35.2-1.1'
sudo apt-mark hold kubelet kubectl

sudo systemctl daemon-reload
sudo systemctl restart kubelet

kubectl get nodes

Worker Node

kubectl drain node01 --ignore-daemonsets

ssh node01

sudo apt-mark unhold kubeadm
sudo apt update
sudo apt install -y kubeadm='1.35.2-1.1'
sudo apt-mark hold kubeadm

sudo kubeadm upgrade node

sudo apt-mark unhold kubelet kubectl
sudo apt install -y kubelet='1.35.2-1.1' kubectl='1.35.2-1.1'
sudo apt-mark hold kubelet kubectl

sudo systemctl daemon-reload
sudo systemctl restart kubelet

exit

kubectl uncordon node01

kubectl get nodes