Kubernetes Cluster

This page documents the Kubernetes cluster configuration and setup details.

Cluster Information

Basic Details

• Kubernetes Version: [e.g., v1.28.2]
• Distribution: [e.g., kubeadm, k3s, microk8s]
• Container Runtime: [e.g., containerd, Docker]
• CNI Plugin: [e.g., Flannel, Calico, Cilium]
• Installation Date: [When cluster was set up]

Cluster Nodes

• Master Nodes: 1
• Worker Nodes: [Number of worker nodes]
• Total Nodes: [Total number of nodes]

# Check cluster info
kubectl cluster-info

# List all nodes
kubectl get nodes -o wide

Control Plane Configuration

Master Node Components

• API Server: Kubernetes API endpoint
• etcd: Cluster state storage
• Controller Manager: Core control loops
• Scheduler: Pod scheduling decisions

Configuration Files

• kubeconfig: ~/.kube/config
• Admin config: /etc/kubernetes/admin.conf
• kubelet config: /etc/kubernetes/kubelet.conf

Worker Node Configuration

Node Components

• kubelet: Node agent
• kube-proxy: Network proxy
• Container Runtime: Container execution

Node Labels and Taints

# View node labels
kubectl get nodes --show-labels

# Add custom labels
kubectl label nodes <node-name> role=worker

# Check taints
kubectl describe nodes | grep Taints

Network Configuration

Pod and Service Networks

• Pod CIDR: [e.g., 10.244.0.0/16]
• Service CIDR: [e.g., 10.96.0.0/12]
• DNS Domain: cluster.local

CNI Configuration

# Example CNI configuration (varies by plugin)
apiVersion: v1
kind: ConfigMap
metadata:
  name: kube-flannel-cfg
  namespace: kube-system
data:
  cni-conf.json: |
    {
      "name": "cbr0",
      "cniVersion": "0.3.1",
      "plugins": [
        {
          "type": "flannel",
          "delegate": {
            "hairpinMode": true,
            "isDefaultGateway": true
          }
        },
        {
          "type": "portmap",
          "capabilities": {
            "portMappings": true
          }
        }
      ]
    }
  net-conf.json: |
    {
      "Network": "10.244.0.0/16",
      "Backend": {
        "Type": "vxlan"
      }
    }

Storage Configuration

Storage Classes

# List storage classes
kubectl get storageclass

# Default storage class
kubectl get storageclass -o yaml

Example Local Storage Class

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: local-storage
  annotations:
    storageclass.kubernetes.io/is-default-class: "true"
provisioner: kubernetes.io/no-provisioner
volumeBindingMode: WaitForFirstConsumer

Security Configuration

RBAC Settings

# Check cluster roles
kubectl get clusterroles

# Check service accounts
kubectl get serviceaccounts --all-namespaces

# View RBAC permissions
kubectl auth can-i --list

Pod Security Standards

# Example pod security policy
apiVersion: policy/v1beta1
kind: PodSecurityPolicy
metadata:
  name: homelab-psp
spec:
  privileged: false
  allowPrivilegeEscalation: false
  requiredDropCapabilities:
    - ALL
  volumes:
    - 'configMap'
    - 'emptyDir'
    - 'projected'
    - 'secret'
    - 'downwardAPI'
    - 'persistentVolumeClaim'
  runAsUser:
    rule: 'MustRunAsNonRoot'
  seLinux:
    rule: 'RunAsAny'
  fsGroup:
    rule: 'RunAsAny'

Namespaces

System Namespaces

• kube-system: Kubernetes system components
• kube-public: Publicly readable cluster info
• kube-node-lease: Node heartbeat information

Application Namespaces

• default: Default application namespace
• test-namespace: Testing and development
• monitoring: Monitoring stack (if deployed)

# List all namespaces
kubectl get namespaces

# Create new namespace
kubectl create namespace my-app

Resource Management

Node Resources

# Check node resource usage
kubectl top nodes

# Describe node resources
kubectl describe node <node-name>

Cluster Resource Quotas

apiVersion: v1
kind: ResourceQuota
metadata:
  name: compute-quota
  namespace: test-namespace
spec:
  hard:
    requests.cpu: "2"
    requests.memory: 4Gi
    limits.cpu: "4"
    limits.memory: 8Gi
    pods: "10"

Limit Ranges

apiVersion: v1
kind: LimitRange
metadata:
  name: default-limits
  namespace: test-namespace
spec:
  limits:
  - default:
      cpu: 100m
      memory: 128Mi
    defaultRequest:
      cpu: 50m
      memory: 64Mi
    type: Container

Monitoring and Logging

Cluster Health Checks

# Check component status
kubectl get componentstatuses

# Check cluster events
kubectl get events --sort-by=.metadata.creationTimestamp

# Check pod logs across cluster
kubectl logs --all-containers=true --tail=100 -l app=my-app

Metrics Collection

• Metrics Server: Resource metrics API
• cAdvisor: Container metrics (built into kubelet)
• Prometheus: (If deployed) Advanced metrics collection

Backup and Recovery

etcd Backup

# Backup etcd (example for kubeadm cluster)
sudo ETCDCTL_API=3 etcdctl snapshot save /backup/etcd-snapshot.db \
  --endpoints=https://127.0.0.1:2379 \
  --cacert=/etc/kubernetes/pki/etcd/ca.crt \
  --cert=/etc/kubernetes/pki/etcd/server.crt \
  --key=/etc/kubernetes/pki/etcd/server.key

Configuration Backup

# Backup all cluster configurations
kubectl get all --all-namespaces -o yaml > cluster-backup.yaml

# Backup specific resources
kubectl get configmaps,secrets --all-namespaces -o yaml > configs-backup.yaml

Maintenance Tasks

Regular Maintenance

• Weekly: Check cluster health and resource usage
• Monthly: Update and patch nodes
• Quarterly: Kubernetes version upgrades

Upgrade Process

# Check upgrade options
kubeadm upgrade plan

# Upgrade control plane
sudo kubeadm upgrade apply v1.28.x

# Upgrade kubelet on nodes
sudo apt update && sudo apt install -y kubelet=1.28.x-00
sudo systemctl daemon-reload
sudo systemctl restart kubelet

Troubleshooting

Common Issues

Node Not Ready

# Check node status
kubectl describe node <node-name>

# Check kubelet logs
sudo journalctl -u kubelet -f

# Restart kubelet
sudo systemctl restart kubelet

Pod Scheduling Issues

# Check scheduler logs
kubectl logs -n kube-system kube-scheduler-<master-node>

# Check node resources
kubectl describe nodes

# Check pod events
kubectl describe pod <pod-name>

Network Issues

# Check CNI pods
kubectl get pods -n kube-system -l app=flannel

# Test pod-to-pod connectivity
kubectl run test-pod --image=busybox --rm -it -- ping <pod-ip>

Performance Tuning

Node Optimization

• CPU: Adjust CPU management policies
• Memory: Configure memory limits appropriately
• I/O: Optimize storage performance

Cluster Settings

# Example kubelet configuration
apiVersion: kubelet.config.k8s.io/v1beta1
kind: KubeletConfiguration
maxPods: 110
podPidsLimit: 2048
evictionHard:
  memory.available: "100Mi"
  nodefs.available: "10%"

Future Plans

Planned Upgrades

• [Kubernetes version upgrades]
• [Add-on installations]
• [Security enhancements]

Scaling Considerations

• [Additional worker nodes]
• [High availability setup]
• [Multi-zone deployment]

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Keep this document updated when making cluster configuration changes.