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Cluster update

This is a guide for updating the Kubernetes version of the cluster.

This document will be similar to the official kubeadm upgrade guide.

Warning

This could change based on kubeadm version! Compare with the guide at the top while updating!

First we are going to connect to the glados control node.

Now we need to change the Kubernetes repo version that we are using.

Run the following command.

sudo vim /etc/apt/sources.list.d/kubernetes.list

In my case, I see:

deb [signed-by=/etc/apt/keyrings/kubernetes-apt-keyring.gpg] https://pkgs.k8s.io/core:/stable:/v1.31/deb/ /

I am going to update from v1.31 to v1.32, so I will change that here.

Press :wq to save this update to the file.

To avoid an error in the sudo apt update, we need to update the signing of the k8s repo:

curl -fsSL https://pkgs.k8s.io/core:/stable:/v1.32/deb/Release.key | sudo gpg --dearmor -o /etc/apt/keyrings/kubernetes-apt-keyring.gpg

Obviously replace v1.32 with your version.

Next we run:

sudo apt update
sudo apt-cache madison kubeadm

This will update all of our package repos to make sure that we are going to download the right versions of everything.

Now we run the following commands:

# replace x in 1.32.x-* with the latest patch version
sudo apt-mark unhold kubeadm && \
sudo apt-get update && sudo apt-get install -y kubeadm='1.32.1-*' && \
sudo apt-mark hold kubeadm

This will update our kubeadm and then hold the version.

Let's verify:

kubeadm version

You should see something like:

kubeadm version: &version.Info{Major:"1", Minor:"32", GitVersion:"v1.32.1", GitCommit:"e9c9be4007d1664e68796af02b8978640d2c1b26", GitTreeState:"clean", BuildDate:"2025-01-15T14:39:14Z", GoVersion:"go1.23.4", Compiler:"gc", Platform:"linux/amd64"}

Now we can verify the upgrade plan:

sudo kubeadm upgrade plan

If all is well, then it is time to upgrade (this command is given in the terminal):

sudo kubeadm upgrade apply v1.32.1

Now we wait... that should eventually say:

[upgrade] SUCCESS! A control plane node of your cluster was upgraded to "v1.32.1".

Now we need to upgrade the nodes:

First connect to the worker node that needs upgrade.

Next upgrade kubeadm again:

# replace x in 1.32.x-* with the latest patch version
sudo apt-mark unhold kubeadm && \
sudo apt-get update && sudo apt-get install -y kubeadm='1.32.x-*' && \
sudo apt-mark hold kubeadm

Now run: 

sudo kubeadm upgrade node

Now we need to drain the node from the control plane:

# execute this command on a control plane node
# replace <node-to-drain> with the name of your node you are draining
kubectl drain <node-to-drain> --ignore-daemonsets

Next:

# replace x in 1.32.x-* with the latest patch version
sudo apt-mark unhold kubelet kubectl && \
sudo apt-get update && sudo apt-get install -y kubelet='1.32.x-*' kubectl='1.32.x-*' && \
sudo apt-mark hold kubelet kubectl

Now restart the kublet:

sudo systemctl daemon-reload
sudo systemctl restart kubelet

Bring the node back:

# execute this command on a control plane node
# replace <node-to-uncordon> with the name of your node
kubectl uncordon <node-to-uncordon>

Repeat this for all of the worker nodes.

Congrats! The cluster is updated.

You can run kubectl get nodes and it will show the version of every node.