Kubernetes Basics

Essential kubectl commands, pod management, and fundamental Kubernetes concepts.

kubectl Basics

Cluster Information

# Check cluster info
kubectl cluster-info

# Get cluster status
kubectl get componentstatuses

# View cluster nodes
kubectl get nodes
kubectl get nodes -o wide

# Show kubectl version
kubectl version
kubectl version --short

# Get current context
kubectl config current-context

# List all contexts
kubectl config get-contexts

# Switch context
kubectl config use-context context-name

Basic Resource Operations

# Get resources
kubectl get pods
kubectl get services
kubectl get deployments
kubectl get all

# Get resources in all namespaces
kubectl get pods --all-namespaces
kubectl get pods -A

# Get resources with labels
kubectl get pods --show-labels
kubectl get pods -l app=nginx

# Get resources with output formats
kubectl get pods -o wide
kubectl get pods -o yaml
kubectl get pods -o json

Resource Description and Details

# Describe resources
kubectl describe pod pod-name
kubectl describe service service-name
kubectl describe node node-name

# Get resource details
kubectl get pod pod-name -o yaml
kubectl get service service-name -o json

# Show resource events
kubectl get events
kubectl get events --sort-by=.metadata.creationTimestamp

Pod Management

Creating Pods

# Create pod from command line
kubectl run nginx --image=nginx
kubectl run busybox --image=busybox --rm -it -- /bin/sh

# Create pod with specific options
kubectl run nginx --image=nginx --port=80 --labels="app=web,env=prod"

# Create pod with resource limits
kubectl run nginx --image=nginx --requests="cpu=100m,memory=128Mi" --limits="cpu=200m,memory=256Mi"

# Create pod in specific namespace
kubectl run nginx --image=nginx -n my-namespace

# Dry run (generate YAML without creating)
kubectl run nginx --image=nginx --dry-run=client -o yaml

Pod Operations

# List pods
kubectl get pods
kubectl get pods -n namespace-name
kubectl get pods --field-selector=status.phase=Running

# Delete pods
kubectl delete pod pod-name
kubectl delete pod pod-name --grace-period=0 --force

# Execute commands in pods
kubectl exec pod-name -- command
kubectl exec -it pod-name -- /bin/bash
kubectl exec -it pod-name -c container-name -- /bin/sh

# Port forwarding
kubectl port-forward pod-name 8080:80
kubectl port-forward pod-name 8080:80 --address=0.0.0.0

# Copy files to/from pods
kubectl cp local-file pod-name:/path/to/file
kubectl cp pod-name:/path/to/file local-file
kubectl cp pod-name:/path/to/file local-file -c container-name

Pod Logs

# View pod logs
kubectl logs pod-name
kubectl logs pod-name -c container-name

# Follow logs
kubectl logs -f pod-name
kubectl logs -f pod-name -c container-name

# Get logs from previous container instance
kubectl logs pod-name --previous

# Get logs with timestamps
kubectl logs pod-name --timestamps

# Get last N lines
kubectl logs pod-name --tail=50

# Get logs since specific time
kubectl logs pod-name --since=1h
kubectl logs pod-name --since=2023-01-01T00:00:00Z

Namespaces

Namespace Operations

# List namespaces
kubectl get namespaces
kubectl get ns

# Create namespace
kubectl create namespace my-namespace

# Delete namespace
kubectl delete namespace my-namespace

# Set default namespace for context
kubectl config set-context --current --namespace=my-namespace

# Get resources in specific namespace
kubectl get pods -n my-namespace
kubectl get all -n my-namespace

Working with Namespaces

# Create resource in namespace
kubectl run nginx --image=nginx -n my-namespace

# Apply manifest to namespace
kubectl apply -f manifest.yaml -n my-namespace

# Get resources across all namespaces
kubectl get pods --all-namespaces
kubectl get pods -A

# Filter by namespace
kubectl get pods --field-selector metadata.namespace=default

YAML Manifests

Basic Pod Manifest

apiVersion: v1
kind: Pod
metadata:
  name: nginx-pod
  labels:
    app: nginx
    env: production
spec:
  containers:
    - name: nginx
      image: nginx:1.20
      ports:
        - containerPort: 80
      resources:
        requests:
          memory: '128Mi'
          cpu: '100m'
        limits:
          memory: '256Mi'
          cpu: '200m'
      env:
        - name: ENV_VAR
          value: 'production'

Multi-Container Pod

apiVersion: v1
kind: Pod
metadata:
  name: multi-container-pod
spec:
  containers:
    - name: web
      image: nginx
      ports:
        - containerPort: 80
      volumeMounts:
        - name: shared-data
          mountPath: /usr/share/nginx/html
    - name: sidecar
      image: busybox
      command:
        [
          'sh',
          '-c',
          'while true; do echo "$(date): Hello from sidecar" > /data/index.html; sleep 10; done',
        ]
      volumeMounts:
        - name: shared-data
          mountPath: /data
  volumes:
    - name: shared-data
      emptyDir: {}

Pod with Volume Mounts

apiVersion: v1
kind: Pod
metadata:
  name: pod-with-volume
spec:
  containers:
    - name: app
      image: nginx
      volumeMounts:
        - name: config-volume
          mountPath: /etc/config
        - name: data-volume
          mountPath: /data
  volumes:
    - name: config-volume
      configMap:
        name: app-config
    - name: data-volume
      persistentVolumeClaim:
        claimName: data-pvc

Labels and Selectors

Working with Labels

# Show labels
kubectl get pods --show-labels
kubectl get nodes --show-labels

# Add labels
kubectl label pod pod-name app=nginx
kubectl label node node-name disk=ssd

# Remove labels
kubectl label pod pod-name app-
kubectl label node node-name disk-

# Update labels
kubectl label pod pod-name app=apache --overwrite

# Select resources by labels
kubectl get pods -l app=nginx
kubectl get pods -l env=production
kubectl get pods -l 'app in (nginx,apache)'
kubectl get pods -l app=nginx,env=production
kubectl get pods -l app!=nginx

Label Selectors

# Equality-based selectors
kubectl get pods -l environment=production
kubectl get pods -l tier!=frontend

# Set-based selectors
kubectl get pods -l 'environment in (production,qa)'
kubectl get pods -l 'tier notin (frontend,backend)'
kubectl get pods -l partition
kubectl get pods -l '!partition'

# Multiple selectors
kubectl get pods -l app=nginx,env=prod
kubectl get pods -l 'app in (nginx,apache),env=prod'

Resource Management

Apply and Create

# Create resources
kubectl create -f manifest.yaml
kubectl create -f directory/
kubectl create -f https://example.com/manifest.yaml

# Apply resources (create or update)
kubectl apply -f manifest.yaml
kubectl apply -f directory/
kubectl apply -R -f directory/  # Recursive

# Apply with record (for rollback)
kubectl apply -f manifest.yaml --record

# Dry run
kubectl apply -f manifest.yaml --dry-run=client
kubectl apply -f manifest.yaml --dry-run=server

Update and Patch

# Replace resource
kubectl replace -f manifest.yaml

# Patch resources
kubectl patch pod pod-name -p '{"spec":{"containers":[{"name":"nginx","image":"nginx:1.21"}]}}'
kubectl patch pod pod-name --type='json' -p='[{"op": "replace", "path": "/spec/containers/0/image", "value":"nginx:1.21"}]'

# Edit resources
kubectl edit pod pod-name
kubectl edit deployment deployment-name

Delete Resources

# Delete by name
kubectl delete pod pod-name
kubectl delete service service-name

# Delete by file
kubectl delete -f manifest.yaml

# Delete by label
kubectl delete pods -l app=nginx

# Delete all pods
kubectl delete pods --all

# Delete with grace period
kubectl delete pod pod-name --grace-period=30
kubectl delete pod pod-name --grace-period=0 --force

# Delete and wait
kubectl delete pod pod-name --wait=true

Quick Reference

Essential Commands

kubectl get pods - List pods
kubectl describe pod name - Pod details
kubectl logs pod-name - View logs
kubectl exec -it pod-name -- /bin/bash - Access pod shell
kubectl apply -f file.yaml - Apply manifest
kubectl delete pod name - Delete pod
kubectl get all - List all resources

Resource Shortcuts

po = pods
svc = services
deploy = deployments
rs = replicasets
cm = configmaps
secrets = secrets
ns = namespaces
pv = persistentvolumes
pvc = persistentvolumeclaims

Common Patterns

# Quick pod for testing
kubectl run test --image=busybox --rm -it -- /bin/sh

# Generate YAML template
kubectl run nginx --image=nginx --dry-run=client -o yaml > pod.yaml

# Watch resources
kubectl get pods -w
kubectl get pods -w -o wide

# Sort by creation time
kubectl get pods --sort-by=.metadata.creationTimestamp

# Custom columns
kubectl get pods -o custom-columns=NAME:.metadata.name,STATUS:.status.phase

Troubleshooting Commands

kubectl describe pod name - Detailed pod information
kubectl logs pod-name - Container logs
kubectl get events - Cluster events
kubectl top pods - Resource usage (requires metrics-server)
kubectl exec -it pod-name -- /bin/bash - Debug inside container

kubectl Basics​

Cluster Information​

Basic Resource Operations​

Resource Description and Details​

Pod Management​

Creating Pods​

Pod Operations​

Pod Logs​

Namespaces​

Namespace Operations​

Working with Namespaces​

YAML Manifests​

Basic Pod Manifest​

Multi-Container Pod​

Pod with Volume Mounts​

Labels and Selectors​

Working with Labels​

Label Selectors​

Resource Management​

Apply and Create​

Update and Patch​

Delete Resources​

Quick Reference​

Essential Commands​

Resource Shortcuts​

Common Patterns​

Troubleshooting Commands​

kubectl Basics

Cluster Information

Basic Resource Operations

Resource Description and Details

Pod Management

Creating Pods

Pod Operations

Pod Logs

Namespaces

Namespace Operations

Working with Namespaces

YAML Manifests

Basic Pod Manifest

Multi-Container Pod

Pod with Volume Mounts

Labels and Selectors

Working with Labels

Label Selectors

Resource Management

Apply and Create

Update and Patch

Delete Resources

Quick Reference

Essential Commands

Resource Shortcuts

Common Patterns

Troubleshooting Commands