Upgrading Kubernetes Control Plane: Best Practices and Commands

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When upgrading the Kubernetes control plane, it is crucial to follow the correct order of component upgrades to ensure a smooth transition. Based on the output from kubeadm upgrade plan, the recommended order is:

1. kube-apiserver

2. kube-controller-manager

3. kube-scheduler

4. kube-proxy

5. CoreDNS

6. etcd

In most cases, `etcd` is upgraded last because there is no change in the current and target version. However, if an `etcd` upgrade is required, it should ideally be done before upgrading the control plane components or worker nodes. This is because newer versions of `etcd` may introduce features that newer Kubernetes components rely on. The `etcd` upgrade typically occurs as a rolling upgrade of `etcd` members in the cluster.

Verified Commands for Kubernetes Control Plane Upgrade

1. Check the current Kubernetes version:

kubectl version --short

2. Check the upgrade plan using kubeadm:

kubeadm upgrade plan

3. Upgrade kubeadm to the target version:

sudo apt-get update && sudo apt-get install -y kubeadm=<target-version>

4. Upgrade the control plane components:

sudo kubeadm upgrade apply <target-version>

5. Upgrade kubelet and kubectl:

sudo apt-get update && sudo apt-get install -y kubelet=<target-version> kubectl=<target-version>

6. Restart the kubelet service:

sudo systemctl daemon-reload
sudo systemctl restart kubelet

7. Verify the upgrade status:

kubectl get nodes

8. Upgrade CoreDNS (if needed):

kubectl -n kube-system get deployment coredns -o yaml > coredns.yaml

<h1>Modify the image version in coredns.yaml</h1>

kubectl apply -f coredns.yaml

9. Upgrade etcd (if required):


<h1>Backup etcd data before upgrading</h1>

etcdctl snapshot save /path/to/snapshot.db

<h1>Upgrade etcd</h1>

sudo apt-get update && sudo apt-get install -y etcd=<target-version>

What Undercode Say

Upgrading the Kubernetes control plane is a critical task that requires careful planning and execution. Following the correct order of component upgrades ensures compatibility and minimizes downtime. Here are some additional Linux and IT-related commands to enhance your Kubernetes management skills:

  • Check system resource usage:
    top

  • Monitor Kubernetes cluster events:

    kubectl get events --sort-by=.metadata.creationTimestamp

  • Check network connectivity between pods:

    kubectl run -it --rm --image=busybox --restart=Never test-pod -- sh

  • View logs of a specific pod:

    kubectl logs <pod-name>

  • Check disk usage on nodes:

    df -h

  • List all running services in the cluster:

    kubectl get services

  • Check the status of kubelet:

    systemctl status kubelet

  • Backup Kubernetes resources:

    kubectl get all --all-namespaces -o yaml > cluster-backup.yaml

  • Restore Kubernetes resources from backup:

    kubectl apply -f cluster-backup.yaml

  • Check for deprecated APIs:

    kubectl api-resources --verbs=list --namespaced -o name | xargs -n 1 kubectl get --show-kind --ignore-not-found -A

For more advanced Kubernetes management, consider exploring the official Kubernetes documentation: https://kubernetes.io/docs/home/.

By following these best practices and commands, you can ensure a seamless upgrade process for your Kubernetes control plane while maintaining the stability and performance of your cluster.

References:

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