Upgrading Homelab Kubernetes Cluster from 1.24 to 1.25

Updating the cluster to match with the latest CKAD exam version.

The Upgrade Path

Our cluster was originally built using Ansible (kubeadm). We will use kubeadm upgrade to upgrade it.

We will be upgrading from:

  1. kubeadm 1.24.6
  2. kubelet 1.24.6
  3. kubectl 1.24.6
  4. kubernetes-cni 1.1.1
  5. coredns 1.8.6
  6. etcd 3.5.3
  7. calico 3.24
  8. containerd 1.6.8
  9. Istio 1.14

to:

  1. kubeadm 1.25.5
  2. kubelet 1.25.5
  3. kubectl 1.25.5
  4. kubernetes-cni 1.1.1
  5. coredns 1.9.3
  6. etcd 3.5.6
  7. calico 3.25
  8. containerd 1.6.8
  9. Istio 1.16

Breaking Changes

PodSecurityPolicy has been removed in v1.25.

Note that policy/v1beta1 PodDisruptionBudget is unavailable in v1.25, use policy/v1 PodDisruptionBudget.

Backup the Cluster

Kubernetes nodes run on KVM, therefore we have taken KVM snapshosts of each virtual machine before starting the upgrade.

Upgrade Control Plane Nodes

Cluster node status before proceeding:

$ kubectl get no -o wide
NAME    STATUS   ROLES           AGE    VERSION   INTERNAL-IP   EXTERNAL-IP   OS-IMAGE                           KERNEL-VERSION              CONTAINER-RUNTIME
srv31   Ready    control-plane   228d   v1.24.6   10.11.1.31    none          Rocky Linux 8.6 (Green Obsidian)   4.18.0-372.9.1.el8.x86_64   containerd://1.6.8
srv32   Ready    control-plane   180d   v1.24.6   10.11.1.32    none          Rocky Linux 8.6 (Green Obsidian)   4.18.0-372.9.1.el8.x86_64   containerd://1.6.8
srv33   Ready    control-plane   309d   v1.24.6   10.11.1.33    none          Rocky Linux 8.6 (Green Obsidian)   4.18.0-372.9.1.el8.x86_64   containerd://1.6.8
srv34   Ready    none            309d   v1.24.6   10.11.1.34    none          Rocky Linux 8.6 (Green Obsidian)   4.18.0-372.9.1.el8.x86_64   containerd://1.6.8
srv35   Ready    none            180d   v1.24.6   10.11.1.35    none          Rocky Linux 8.6 (Green Obsidian)   4.18.0-372.9.1.el8.x86_64   containerd://1.6.8
srv36   Ready    none            309d   v1.24.6   10.11.1.36    none          Rocky Linux 8.6 (Green Obsidian)   4.18.0-372.9.1.el8.x86_64   containerd://1.6.8

Perform kubeadm upgrade

The upgrade procedure on control plane nodes should be executed one node at a time.

We will start with the control plane srv31. For the first control plane node srv31:

$ sudo yum install -y kubeadm-1.25.5-0 --disableexcludes=kubernetes
$ kubeadm version

Verify the upgrade plan:

$ sudo kubeadm upgrade plan
[upgrade/config] Making sure the configuration is correct:
[upgrade/config] Reading configuration from the cluster...
[upgrade/config] FYI: You can look at this config file with 'kubectl -n kube-system get cm kubeadm-config -o yaml'
[upload-config] Storing the configuration used in ConfigMap "kubeadm-config" in the "kube-system" Namespace
[preflight] Running pre-flight checks.
[upgrade] Running cluster health checks
[upgrade] Fetching available versions to upgrade to
[upgrade/versions] Cluster version: v1.24.6
[upgrade/versions] kubeadm version: v1.25.5
I0118 15:13:14.565296  116046 version.go:256] remote version is much newer: v1.26.0; falling back to: stable-1.25
[upgrade/versions] Target version: v1.25.5
[upgrade/versions] Latest version in the v1.24 series: v1.24.9

Components that must be upgraded manually after you have upgraded the control plane with 'kubeadm upgrade apply':
COMPONENT   CURRENT       TARGET
kubelet     6 x v1.24.6   v1.24.9

Upgrade to the latest version in the v1.24 series:

COMPONENT                 CURRENT   TARGET
kube-apiserver            v1.24.6   v1.24.9
kube-controller-manager   v1.24.6   v1.24.9
kube-scheduler            v1.24.6   v1.24.9
kube-proxy                v1.24.6   v1.24.9
CoreDNS                   v1.8.6    v1.9.3
etcd                      3.5.3-0   3.5.6-0

You can now apply the upgrade by executing the following command:

	kubeadm upgrade apply v1.24.9

_____________________________________________________________________

Components that must be upgraded manually after you have upgraded the control plane with 'kubeadm upgrade apply':
COMPONENT   CURRENT       TARGET
kubelet     6 x v1.24.6   v1.25.5

Upgrade to the latest stable version:

COMPONENT                 CURRENT   TARGET
kube-apiserver            v1.24.6   v1.25.5
kube-controller-manager   v1.24.6   v1.25.5
kube-scheduler            v1.24.6   v1.25.5
kube-proxy                v1.24.6   v1.25.5
CoreDNS                   v1.8.6    v1.9.3
etcd                      3.5.3-0   3.5.6-0

You can now apply the upgrade by executing the following command:

	kubeadm upgrade apply v1.25.5


The table below shows the current state of component configs as understood by this version of kubeadm.
Configs that have a "yes" mark in the "MANUAL UPGRADE REQUIRED" column require manual config upgrade or
resetting to kubeadm defaults before a successful upgrade can be performed. The version to manually
upgrade to is denoted in the "PREFERRED VERSION" column.

API GROUP                 CURRENT VERSION   PREFERRED VERSION   MANUAL UPGRADE REQUIRED
kubeproxy.config.k8s.io   v1alpha1          v1alpha1            no
kubelet.config.k8s.io     v1beta1           v1beta1             no
_____________________________________________________________________________________________________________________________

Upgrade the cluster:

$ sudo kubeadm upgrade apply v1.25.5
[upgrade/config] Making sure the configuration is correct:
[upgrade/config] Reading configuration from the cluster...
[upgrade/config] FYI: You can look at this config file with 'kubectl -n kube-system get cm kubeadm-config -o yaml'
[preflight] Running pre-flight checks.
[upgrade] Running cluster health checks
[upgrade/version] You have chosen to change the cluster version to "v1.25.5"
[upgrade/versions] Cluster version: v1.24.6
[upgrade/versions] kubeadm version: v1.25.5
[upgrade] Are you sure you want to proceed? [y/N]: y
[upgrade/prepull] Pulling images required for setting up a Kubernetes cluster
[upgrade/prepull] This might take a minute or two, depending on the speed of your internet connection
[upgrade/prepull] You can also perform this action in beforehand using 'kubeadm config images pull'
[upgrade/apply] Upgrading your Static Pod-hosted control plane to version "v1.25.5" (timeout: 5m0s)...
[upgrade/etcd] Upgrading to TLS for etcd
[upgrade/staticpods] Preparing for "etcd" upgrade
[upgrade/staticpods] Renewing etcd-server certificate
[upgrade/staticpods] Renewing etcd-peer certificate
[upgrade/staticpods] Renewing etcd-healthcheck-client certificate
[upgrade/staticpods] Moved new manifest to "/etc/kubernetes/manifests/etcd.yaml" and backed up old manifest to "/etc/kubernetes/tmp/kubeadm-backup-manifests-2023-01-18-15-21-43/etcd.yaml"
[upgrade/staticpods] Waiting for the kubelet to restart the component
[upgrade/staticpods] This might take a minute or longer depending on the component/version gap (timeout 5m0s)
[apiclient] Found 3 Pods for label selector component=etcd
[upgrade/staticpods] Component "etcd" upgraded successfully!
[upgrade/etcd] Waiting for etcd to become available
[upgrade/staticpods] Writing new Static Pod manifests to "/etc/kubernetes/tmp/kubeadm-upgraded-manifests3785479248"
[upgrade/staticpods] Preparing for "kube-apiserver" upgrade
[upgrade/staticpods] Renewing apiserver certificate
[upgrade/staticpods] Renewing apiserver-kubelet-client certificate
[upgrade/staticpods] Renewing front-proxy-client certificate
[upgrade/staticpods] Renewing apiserver-etcd-client certificate
[upgrade/staticpods] Moved new manifest to "/etc/kubernetes/manifests/kube-apiserver.yaml" and backed up old manifest to "/etc/kubernetes/tmp/kubeadm-backup-manifests-2023-01-18-15-21-43/kube-apiserver.yaml"
[upgrade/staticpods] Waiting for the kubelet to restart the component
[upgrade/staticpods] This might take a minute or longer depending on the component/version gap (timeout 5m0s)
[apiclient] Found 3 Pods for label selector component=kube-apiserver
[upgrade/staticpods] Component "kube-apiserver" upgraded successfully!
[upgrade/staticpods] Preparing for "kube-controller-manager" upgrade
[upgrade/staticpods] Renewing controller-manager.conf certificate
[upgrade/staticpods] Moved new manifest to "/etc/kubernetes/manifests/kube-controller-manager.yaml" and backed up old manifest to "/etc/kubernetes/tmp/kubeadm-backup-manifests-2023-01-18-15-21-43/kube-controller-manager.yaml"
[upgrade/staticpods] Waiting for the kubelet to restart the component
[upgrade/staticpods] This might take a minute or longer depending on the component/version gap (timeout 5m0s)
[apiclient] Found 3 Pods for label selector component=kube-controller-manager
[upgrade/staticpods] Component "kube-controller-manager" upgraded successfully!
[upgrade/staticpods] Preparing for "kube-scheduler" upgrade
[upgrade/staticpods] Renewing scheduler.conf certificate
[upgrade/staticpods] Moved new manifest to "/etc/kubernetes/manifests/kube-scheduler.yaml" and backed up old manifest to "/etc/kubernetes/tmp/kubeadm-backup-manifests-2023-01-18-15-21-43/kube-scheduler.yaml"
[upgrade/staticpods] Waiting for the kubelet to restart the component
[upgrade/staticpods] This might take a minute or longer depending on the component/version gap (timeout 5m0s)
[apiclient] Found 3 Pods for label selector component=kube-scheduler
[upgrade/staticpods] Component "kube-scheduler" upgraded successfully!
[upgrade/postupgrade] Removing the old taint &Taint{Key:node-role.kubernetes.io/master,Value:,Effect:NoSchedule,TimeAdded:,} from all control plane Nodes. After this step only the &Taint{Key:node-role.kubernetes.io/control-plane,Value:,Effect:NoSchedule,TimeAdded:,} taint will be present on control plane Nodes.
[upload-config] Storing the configuration used in ConfigMap "kubeadm-config" in the "kube-system" Namespace
[kubelet] Creating a ConfigMap "kubelet-config" in namespace kube-system with the configuration for the kubelets in the cluster
[kubelet-start] Writing kubelet configuration to file "/var/lib/kubelet/config.yaml"
[bootstrap-token] Configured RBAC rules to allow Node Bootstrap tokens to get nodes
[bootstrap-token] Configured RBAC rules to allow Node Bootstrap tokens to post CSRs in order for nodes to get long term certificate credentials
[bootstrap-token] Configured RBAC rules to allow the csrapprover controller automatically approve CSRs from a Node Bootstrap Token
[bootstrap-token] Configured RBAC rules to allow certificate rotation for all node client certificates in the cluster
[addons] Applied essential addon: CoreDNS
[addons] Applied essential addon: kube-proxy

[upgrade/successful] SUCCESS! Your cluster was upgraded to "v1.25.5". Enjoy!

[upgrade/kubelet] Now that your control plane is upgraded, please proceed with upgrading your kubelets if you haven't already done so.

We need to upgrade our CNI provider plugin. We are going to upgrade to Calico 3.25 which has been tested against Kubernetes version 1.24.

$ kubectl apply -f https://docs.projectcalico.org/archive/v3.25/manifests/calico.yaml
poddisruptionbudget.policy/calico-kube-controllers configured
serviceaccount/calico-kube-controllers unchanged
serviceaccount/calico-node unchanged
configmap/calico-config unchanged
customresourcedefinition.apiextensions.k8s.io/bgpconfigurations.crd.projectcalico.org configured
customresourcedefinition.apiextensions.k8s.io/bgppeers.crd.projectcalico.org configured
customresourcedefinition.apiextensions.k8s.io/blockaffinities.crd.projectcalico.org configured
customresourcedefinition.apiextensions.k8s.io/caliconodestatuses.crd.projectcalico.org configured
customresourcedefinition.apiextensions.k8s.io/clusterinformations.crd.projectcalico.org configured
customresourcedefinition.apiextensions.k8s.io/felixconfigurations.crd.projectcalico.org configured
customresourcedefinition.apiextensions.k8s.io/globalnetworkpolicies.crd.projectcalico.org configured
customresourcedefinition.apiextensions.k8s.io/globalnetworksets.crd.projectcalico.org configured
customresourcedefinition.apiextensions.k8s.io/hostendpoints.crd.projectcalico.org configured
customresourcedefinition.apiextensions.k8s.io/ipamblocks.crd.projectcalico.org configured
customresourcedefinition.apiextensions.k8s.io/ipamconfigs.crd.projectcalico.org configured
customresourcedefinition.apiextensions.k8s.io/ipamhandles.crd.projectcalico.org configured
customresourcedefinition.apiextensions.k8s.io/ippools.crd.projectcalico.org configured
customresourcedefinition.apiextensions.k8s.io/ipreservations.crd.projectcalico.org configured
customresourcedefinition.apiextensions.k8s.io/kubecontrollersconfigurations.crd.projectcalico.org configured
customresourcedefinition.apiextensions.k8s.io/networkpolicies.crd.projectcalico.org configured
customresourcedefinition.apiextensions.k8s.io/networksets.crd.projectcalico.org configured
clusterrole.rbac.authorization.k8s.io/calico-kube-controllers unchanged
clusterrole.rbac.authorization.k8s.io/calico-node configured
clusterrolebinding.rbac.authorization.k8s.io/calico-kube-controllers unchanged
clusterrolebinding.rbac.authorization.k8s.io/calico-node unchanged
daemonset.apps/calico-node configured
deployment.apps/calico-kube-controllers configured

For the other control plane nodes:

$ sudo yum install -y kubeadm-1.25.5-0 --disableexcludes=kubernetes
$ kubeadm version
$ sudo kubeadm config images pull
$ sudo kubeadm upgrade node

According to Kubernetes documentation, calling kubeadm upgrade plan and upgrading the CNI provider plugin is no longer needed.

Drain the Nodes and Upgrade kubelet and kubectl

$ export CONTROL_PLANE="srv31"
$ kubectl drain ${CONTROL_PLANE} --ignore-daemonsets --delete-emptydir-data
$ sudo yum install -y kubelet-1.25.5-0 kubectl-1.25.5-0 --disableexcludes=kubernetes
$ sudo systemctl daemon-reload && sudo systemctl restart kubelet
$ kubectl uncordon ${CONTROL_PLANE}

Upgrade Worker Nodes

We will start with the worker node srv34.

Upgrade kubeadm:

$ sudo yum install -y kubeadm-1.25.5-0 --disableexcludes=kubernetes
$ sudo kubeadm upgrade node

Drain the worker node:

$ export WORKER_NODE="srv34"
$ kubectl drain ${WORKER_NODE} --ignore-daemonsets --delete-emptydir-data

Upgrade kubelet and kubectl:

$ sudo yum install -y kubelet-1.25.5-0 kubectl-1.25.5-0 --disableexcludes=kubernetes
$ sudo systemctl daemon-reload && sudo systemctl restart kubelet

Uncordon the worker node:

$ kubectl uncordon ${WORKER_NODE}

Repeat the process for worker nodes srv35 and srv36.

Verify Cluster Status

Check cluster node status:

$ kubectl get no
NAME    STATUS   ROLES           AGE    VERSION
srv31   Ready    control-plane   228d   v1.25.5
srv32   Ready    control-plane   180d   v1.25.5
srv33   Ready    control-plane   309d   v1.25.5
srv34   Ready    none            309d   v1.25.5
srv35   Ready    none            180d   v1.25.5
srv36   Ready    none            309d   v1.25.5

Check Calico pods:

$ kubectl -n kube-system get po -l k8s-app=calico-node
NAME                READY   STATUS    RESTARTS   AGE
calico-node-9mnwg   1/1     Running   0          15m
calico-node-b8jk5   1/1     Running   0          19m
calico-node-gzcnx   1/1     Running   0          19m
calico-node-p2xt5   1/1     Running   0          18m
calico-node-rd6h6   1/1     Running   0          16m
calico-node-rzm6w   1/1     Running   0          17m

Update Istio

Istio Canary updates are not great because they don’t upgrade sidecars. In production we build a new Kubernetes cluster using red/black deployment and install a new version of Istio. For the purpose of the homelab environment, we will do an in-place upgrade.

Download istioctl binary:

$ curl -fsSL -o istioctl.tar.gz https://github.com/istio/istio/releases/download/1.16.1/istioctl-1.16.1-linux-amd64.tar.gz
$ tar xf istioctl.tar.gz
$ sudo mv istioctl /usr/local/bin/
$ sudo chown root: /usr/local/bin/istioctl

Ensure that the upgrade is compatible with our environment:

$ istioctl x precheck
✔ No issues found when checking the cluster. Istio is safe to install or upgrade!
$ istioctl version
client version: 1.16.1
control plane version: 1.14.4
data plane version: 1.14.4 (15 proxies)

Generate a YAML manifest for Kubernetes:

$ git clone https://github.com/lisenet/kubernetes-homelab.git
$ cd ./kubernetes-homelab/istio
$ istioctl manifest generate --cluster-specific -f ./istio-operator.yml > ./istio-kubernetes.yml

Upgrade Istio. The kubectl apply command may show transient errors due to resources not being available in the cluster in the correct order. If that happens, simply run the command again.

$ kubectl apply -f ./istio-kubernetes.yml

Verify:

$ istioctl verify-install -f ./istio-kubernetes.yml
$ kubectl get po -n istio-system
NAME                                   READY   STATUS    RESTARTS   AGE
istio-ingressgateway-7f56f556b-9vjsp   1/1     Running   0          6m13s
istio-ingressgateway-7f56f556b-pxmbb   1/1     Running   0          6m13s
istiod-5bbc6f64bc-lcv45                1/1     Running   0          6m13s
kiali-c946fb5bc-lqzgl                  1/1     Running   0          17m
prometheus-6d496598f9-fksjp            2/2     Running   0          17m

We should see the updated version on the control plane but a bunch of old proxies (sidecars) on the data plane:

$ istioctl version
client version: 1.16.1
control plane version: 1.16.1
data plane version: 1.14.4 (2 proxies), 1.16.1 (13 proxies)

Restart all pods that have Istio sidecards running to allow them to pick up a new version of Istio. When done, we should have no old versions of proxies running:

$ istioctl version
client version: 1.16.1
control plane version: 1.16.1
data plane version: 1.16.1 (15 proxies)

References

https://kubernetes.io/docs/tasks/administer-cluster/kubeadm/kubeadm-upgrade/

https://istio.io/latest/docs/setup/upgrade/in-place/

https://github.com/istio/istio/issues/42423

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