Kubernetes / OpenShift Cluster Operations

Day-2 operations, maintenance, and lifecycle management for production clusters.

Current Versions & Documentation (January 2026)

| Platform | Current Version | Upgrade Path | Documentation | |----------|-----------------|--------------|---------------| | Kubernetes | 1.31.x | 1.30 → 1.31 | https://kubernetes.io/docs/tasks/administer-cluster/ | | OpenShift | 4.17.x | 4.16 → 4.17 | https://docs.openshift.com/container-platform/4.17/ | | EKS | 1.31 | Rolling updates | https://docs.aws.amazon.com/eks/latest/userguide/update-cluster.html | | AKS | 1.31 | Blue-green or rolling | https://learn.microsoft.com/azure/aks/upgrade-cluster | | GKE | 1.31 | Surge upgrades | https://cloud.google.com/kubernetes-engine/docs/how-to/upgrading-a-cluster |

Key Tools & Versions

| Tool | Version | Install | Purpose | |------|---------|---------|--------| | kubeadm | 1.31.x | Package manager | Cluster bootstrap | | Velero | 1.15.x | Helm/CLI | Backup & restore | | kube-prometheus-stack | v67.x | Helm | Monitoring | | VPA | 1.3.x | kubectl apply | Vertical scaling | | Cluster Autoscaler | 1.31.x | Helm | Node autoscaling | | Karpenter | 1.1.x | Helm | AWS node provisioning |

Command Usage Convention

IMPORTANT: This skill uses kubectl as the primary command. When working with:

• OpenShift/ARO clusters: Replace kubectl with oc
• Standard Kubernetes (AKS, EKS, GKE): Use kubectl as shown

Node Operations

Node Lifecycle

# View node status
kubectl get nodes -o wide

# Detailed node info
kubectl describe node ${NODE_NAME}

# Check node resources
kubectl top nodes

# Node labels and taints
kubectl get nodes --show-labels
kubectl describe node ${NODE} | grep -A 5 Taints

Drain and Cordon

# Cordon: Mark node unschedulable (no new pods)
kubectl cordon ${NODE_NAME}

# Drain: Evict pods safely
kubectl drain ${NODE_NAME} \
  --ignore-daemonsets \
  --delete-emptydir-data \
  --grace-period=60 \
  --timeout=300s

# Force drain (use with caution)
kubectl drain ${NODE_NAME} \
  --ignore-daemonsets \
  --delete-emptydir-data \
  --force \
  --grace-period=30

# Uncordon: Allow scheduling again
kubectl uncordon ${NODE_NAME}

Cluster Autoscaler Configuration

apiVersion: apps/v1
kind: Deployment
metadata:
  name: cluster-autoscaler
  namespace: kube-system
spec:
  template:
    spec:
      containers:
        - name: cluster-autoscaler
          image: registry.k8s.io/autoscaling/cluster-autoscaler:v1.31.0
          command:
            - ./cluster-autoscaler
            - --v=4
            - --cloud-provider=${CLOUD_PROVIDER}
            - --nodes=${MIN}:${MAX}:${NODE_GROUP}
            - --scale-down-delay-after-add=10m
            - --scale-down-unneeded-time=10m
            - --scale-down-utilization-threshold=0.5
            - --skip-nodes-with-local-storage=false
            - --skip-nodes-with-system-pods=true
            - --balance-similar-node-groups=true

Backup and Recovery

etcd Backup

# Backup etcd (run on control plane node)
ETCDCTL_API=3 etcdctl snapshot save /backup/etcd-$(date +%Y%m%d-%H%M%S).db \
  --endpoints=https://127.0.0.1:2379 \
  --cacert=/etc/kubernetes/pki/etcd/ca.crt \
  --cert=/etc/kubernetes/pki/etcd/healthcheck-client.crt \
  --key=/etc/kubernetes/pki/etcd/healthcheck-client.key

# Verify backup
ETCDCTL_API=3 etcdctl snapshot status /backup/etcd-snapshot.db --write-out=table

Velero Backup (v1.15.x)

# Install Velero CLI
brew install velero

# Install Velero server with AWS provider
velero install \
  --provider aws \
  --bucket ${BUCKET_NAME} \
  --secret-file ./credentials-velero \
  --backup-location-config region=${REGION} \
  --snapshot-location-config region=${REGION} \
  --plugins velero/velero-plugin-for-aws:v1.10.0 \
  --use-node-agent

# Create backup
velero backup create ${BACKUP_NAME} \
  --include-namespaces ${NAMESPACES} \
  --ttl 720h \
  --default-volumes-to-fs-backup

# Create scheduled backup
velero schedule create daily-backup \
  --schedule="0 2 * * *" \
  --include-namespaces ${NAMESPACES} \
  --ttl 168h

# Restore from backup
velero restore create --from-backup ${BACKUP_NAME}

Velero Backup Manifest

apiVersion: velero.io/v1
kind: Backup
metadata:
  name: ${BACKUP_NAME}
  namespace: velero
spec:
  includedNamespaces:
    - ${NAMESPACE_1}
    - ${NAMESPACE_2}
  excludedResources:
    - events
    - events.events.k8s.io
  storageLocation: default
  volumeSnapshotLocations:
    - default
  ttl: 720h0m0s
  snapshotVolumes: true
  hooks:
    resources:
      - name: backup-hook
        includedNamespaces:
          - ${NAMESPACE}
        labelSelector:
          matchLabels:
            app: database
        pre:
          - exec:
              container: database
              command:
                - /bin/sh
                - -c
                - "pg_dump -U postgres > /backup/pre-backup.sql"
              onError: Fail
              timeout: 120s

Cluster Upgrades

Pre-Upgrade Checklist

#!/bin/bash
# pre-upgrade-check.sh

echo "=== Cluster Version ==="
kubectl version --short

echo -e "\n=== Node Status ==="
kubectl get nodes

echo -e "\n=== Pods Not Running ==="
kubectl get pods -A --field-selector=status.phase!=Running,status.phase!=Succeeded

echo -e "\n=== PDBs That May Block Drain ==="
kubectl get pdb -A

echo -e "\n=== Pending PVCs ==="
kubectl get pvc -A --field-selector=status.phase=Pending

echo -e "\n=== Deprecated APIs in Use ==="
kubectl get --raw /metrics | grep apiserver_requested_deprecated_apis

AKS Upgrade (Azure)

# Check current version and available upgrades
az aks get-versions --location ${LOCATION} -o table
az aks get-upgrades --resource-group ${RG} --name ${CLUSTER} -o table

# Upgrade control plane and node pools
az aks upgrade --resource-group ${RG} --name ${CLUSTER} \
  --kubernetes-version 1.31.0

# Use blue-green upgrade with max surge
az aks nodepool upgrade --resource-group ${RG} --cluster-name ${CLUSTER} \
  --name ${NODEPOOL} --kubernetes-version 1.31.0 \
  --max-surge 33%

# Enable auto-upgrade channel
az aks update --resource-group ${RG} --name ${CLUSTER} \
  --auto-upgrade-channel stable

EKS Upgrade

# Update control plane
aws eks update-cluster-version \
  --name ${CLUSTER_NAME} \
  --kubernetes-version 1.31

# Wait for completion
aws eks wait cluster-active --name ${CLUSTER_NAME}

# Update EKS add-ons
for addon in vpc-cni coredns kube-proxy eks-pod-identity-agent; do
  aws eks update-addon --cluster-name ${CLUSTER_NAME} \
    --addon-name $addon \
    --resolve-conflicts PRESERVE
done

# Update managed node groups
aws eks update-nodegroup-version \
  --cluster-name ${CLUSTER_NAME} \
  --nodegroup-name ${NODEGROUP_NAME}

GKE Upgrade

# Check available versions
gcloud container get-server-config --region ${REGION}

# Upgrade control plane
gcloud container clusters upgrade ${CLUSTER} --region ${REGION} \
  --master --cluster-version 1.31

# Upgrade node pools
gcloud container clusters upgrade ${CLUSTER} --region ${REGION} \
  --node-pool ${POOL} \
  --cluster-version 1.31

# Enable release channel
gcloud container clusters update ${CLUSTER} --region ${REGION} \
  --release-channel regular

OpenShift Upgrade

# Check available updates
oc adm upgrade

# View current version and channel
oc get clusterversion
oc get clusterversion version -o jsonpath='{.spec.channel}'

# Change channel
oc adm upgrade channel stable-4.17

# Start upgrade
oc adm upgrade --to-latest
# OR upgrade to specific version
oc adm upgrade --to=4.17.5

# Monitor upgrade progress
watch -n 10 'oc get clusterversion && oc get clusteroperators'

Resource Management

Resource Quotas

apiVersion: v1
kind: ResourceQuota
metadata:
  name: compute-quota
  namespace: ${NAMESPACE}
spec:
  hard:
    requests.cpu: "10"
    requests.memory: 20Gi
    limits.cpu: "20"
    limits.memory: 40Gi
    pods: "50"
    persistentvolumeclaims: "10"
    requests.storage: 100Gi

Limit Ranges

apiVersion: v1
kind: LimitRange
metadata:
  name: default-limits
  namespace: ${NAMESPACE}
spec:
  limits:
    - type: Container
      default:
        cpu: 500m
        memory: 512Mi
      defaultRequest:
        cpu: 100m
        memory: 128Mi
      max:
        cpu: "4"
        memory: 8Gi
      min:
        cpu: 50m
        memory: 64Mi

Check Resource Usage

# Namespace resource usage vs quota
kubectl describe quota -n ${NAMESPACE}

# Pod resource usage
kubectl top pods -n ${NAMESPACE} --sort-by=memory
kubectl top pods -n ${NAMESPACE} --sort-by=cpu

# Node resource allocation
kubectl describe nodes | grep -A 5 "Allocated resources"

Certificate Management

Check Certificate Expiry

# kubeadm certificates
kubeadm certs check-expiration

# Manual check
openssl x509 -in /etc/kubernetes/pki/apiserver.crt -noout -dates

# Check all certs
for cert in /etc/kubernetes/pki/*.crt; do
  echo "=== $cert ==="
  openssl x509 -in $cert -noout -dates
done

Rotate Certificates

# Renew all certificates (kubeadm)
kubeadm certs renew all

# Restart control plane components
crictl pods --name kube-apiserver -q | xargs crictl stopp
crictl pods --name kube-controller-manager -q | xargs crictl stopp
crictl pods --name kube-scheduler -q | xargs crictl stopp

Monitoring Setup

Prometheus Stack (kube-prometheus-stack v67.x)

# Add Helm repo
helm repo add prometheus-community https://prometheus-community.github.io/helm-charts
helm repo update

# Install
helm upgrade --install prometheus prometheus-community/kube-prometheus-stack \
  --namespace monitoring \
  --create-namespace \
  --set prometheus.prometheusSpec.retention=30d \
  --set prometheus.prometheusSpec.replicas=2 \
  --set prometheus.prometheusSpec.resources.requests.memory=2Gi \
  --set alertmanager.alertmanagerSpec.replicas=3 \
  --set grafana.persistence.enabled=true

# Access Grafana
kubectl port-forward -n monitoring svc/prometheus-grafana 3000:80

Custom ServiceMonitor

apiVersion: monitoring.coreos.com/v1
kind: ServiceMonitor
metadata:
  name: ${APP_NAME}
  namespace: monitoring
  labels:
    release: prometheus
spec:
  namespaceSelector:
    matchNames:
      - ${NAMESPACE}
  selector:
    matchLabels:
      app.kubernetes.io/name: ${APP_NAME}
  endpoints:
    - port: metrics
      interval: 30s
      path: /metrics

Cost Optimization

VerticalPodAutoscaler

apiVersion: autoscaling.k8s.io/v1
kind: VerticalPodAutoscaler
metadata:
  name: ${APP_NAME}-vpa
  namespace: ${NAMESPACE}
spec:
  targetRef:
    apiVersion: apps/v1
    kind: Deployment
    name: ${APP_NAME}
  updatePolicy:
    updateMode: "Auto"
  resourcePolicy:
    containerPolicies:
      - containerName: "*"
        minAllowed:
          cpu: 50m
          memory: 64Mi
        maxAllowed:
          cpu: 4
          memory: 8Gi

Namespace Lifecycle

Namespace Template

apiVersion: v1
kind: Namespace
metadata:
  name: ${NAMESPACE}
  labels:
    app.kubernetes.io/managed-by: cluster-skills
    environment: ${ENVIRONMENT}
    team: ${TEAM}
  annotations:
    owner: ${OWNER_EMAIL}
---
apiVersion: v1
kind: ResourceQuota
metadata:
  name: default-quota
  namespace: ${NAMESPACE}
spec:
  hard:
    requests.cpu: "10"
    requests.memory: 20Gi
    limits.cpu: "20"
    limits.memory: 40Gi
    pods: "50"
---
apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: default-deny
  namespace: ${NAMESPACE}
spec:
  podSelector: {}
  policyTypes:
    - Ingress
    - Egress

Disaster Recovery

Full Cluster Recovery Checklist

1. Restore etcd - See etcd restore section
2. Verify Control Plane

   kubectl get nodes
   kubectl get pods -n kube-system
   kubectl cluster-info
   

3. Restore Workloads (Velero)

   velero restore create --from-backup ${BACKUP_NAME}
   

4. Verify Application Health

   kubectl get pods -A
   kubectl get svc -A
   

5. Verify DNS and Networking

   kubectl run dns-test --image=busybox --rm -it --restart=Never -- nslookup kubernetes