kubectl and k9s essentials¶

Duration: 65 minutes (35 minutes theory + 30 minutes lab)

Learning Objectives¶

Master essential kubectl commands
Learn kubectl productivity tips and shortcuts
Understand kubectl context and configuration
Use k9s for visual cluster management
Debug and troubleshoot common issues
Efficiently navigate and inspect cluster resources

kubectl Basics¶

kubectl is the primary CLI tool for interacting with Kubernetes clusters.

Command Structure¶

kubectl [command] [TYPE] [NAME] [flags]

Examples:

kubectl get pods
kubectl describe pod nginx
kubectl delete deployment web
kubectl logs nginx -f

Essential Commands¶

Command	Purpose	Example
`get`	List resources	`kubectl get pods`
`describe`	Show detailed info	`kubectl describe pod nginx`
`create`	Create resource	`kubectl create deployment nginx --image=nginx`
`apply`	Apply configuration	`kubectl apply -f app.yaml`
`delete`	Delete resources	`kubectl delete pod nginx`
`logs`	View logs	`kubectl logs nginx -f`
`exec`	Execute command	`kubectl exec -it nginx -- bash`
`port-forward`	Forward ports	`kubectl port-forward pod/nginx 8080:80`
`edit`	Edit resource	`kubectl edit deployment nginx`
`scale`	Scale replicas	`kubectl scale deployment nginx --replicas=3`

kubectl get - List Resources¶

# List pods
kubectl get pods
kubectl get pods -o wide          # More details (node, IP)
kubectl get pods -o yaml          # Full YAML output
kubectl get pods -o json          # JSON output
kubectl get pods -o name          # Just names

# List all resource types
kubectl get all

# List across all namespaces
kubectl get pods --all-namespaces
kubectl get pods -A               # Short form

# Filter by labels
kubectl get pods -l app=nginx
kubectl get pods -l 'app=nginx,env=prod'
kubectl get pods -l 'env!=dev'

# Watch for changes
kubectl get pods -w
kubectl get pods --watch

# Sort by field
kubectl get pods --sort-by=.metadata.creationTimestamp
kubectl get pods --sort-by=.status.startTime

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

kubectl describe - Detailed Information¶

# Describe pod (shows events!)
kubectl describe pod nginx

# Describe multiple resources
kubectl describe pods -l app=nginx

# Describe node
kubectl describe node kind-worker

# Describe service
kubectl describe service nginx

Key information shown:

Configuration details
Status and conditions
Events (creations, errors, scheduling)
Resource usage
Volume mounts

kubectl logs - View Logs¶

# View pod logs
kubectl logs nginx

# Follow logs (like tail -f)
kubectl logs -f nginx

# Logs from previous container instance
kubectl logs nginx --previous

# Logs from specific container in multi-container pod
kubectl logs nginx -c sidecar

# Last N lines
kubectl logs nginx --tail=50

# Logs since timestamp
kubectl logs nginx --since=1h
kubectl logs nginx --since-time=2024-01-01T00:00:00Z

# All pods matching label
kubectl logs -l app=nginx --all-containers=true

# Combine with grep
kubectl logs nginx | grep ERROR

kubectl exec - Execute Commands¶

# Interactive shell
kubectl exec -it nginx -- /bin/sh
kubectl exec -it nginx -- /bin/bash

# Run single command
kubectl exec nginx -- ls /etc
kubectl exec nginx -- cat /etc/nginx/nginx.conf

# Specific container in multi-container pod
kubectl exec -it nginx -c sidecar -- sh

# Run command in all pods
kubectl get pods -l app=nginx -o name | \
  xargs -I {} kubectl exec {} -- date

kubectl apply vs create¶

# create: Create new resource (fails if exists)
kubectl create -f app.yaml

# apply: Create or update resource (idempotent)
kubectl apply -f app.yaml

# apply is declarative and tracks changes
kubectl apply -f app.yaml --dry-run=client  # Preview
kubectl apply -f app.yaml --dry-run=server  # Validate with server

# Apply directory of manifests
kubectl apply -f ./manifests/

# Apply with kustomize
kubectl apply -k ./overlays/production/

kubectl port-forward - Access Services Locally¶

# Forward pod port to localhost
kubectl port-forward pod/nginx 8080:80

# Forward service port
kubectl port-forward service/nginx 8080:80

# Forward deployment port
kubectl port-forward deployment/nginx 8080:80

# Bind to specific address
kubectl port-forward --address 0.0.0.0 pod/nginx 8080:80

# Multiple ports
kubectl port-forward pod/nginx 8080:80 8443:443

Access at: http://localhost:8080

kubectl Context and Configuration¶

# View current context
kubectl config current-context

# List all contexts
kubectl config get-contexts

# Switch context
kubectl config use-context kind-kind

# View full config
kubectl config view

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

# Create new context
kubectl config set-context dev --cluster=kind-kind --user=kind-kind --namespace=development

kubectl Shortcuts and Aliases¶

# Enable kubectl autocompletion
source <(kubectl completion bash)
echo "source <(kubectl completion bash)" >> ~/.bashrc

# Alias k=kubectl
alias k=kubectl
complete -F __start_kubectl k

# Common aliases
alias kgp='kubectl get pods'
alias kgs='kubectl get svc'
alias kgd='kubectl get deployments'
alias kd='kubectl describe'
alias kl='kubectl logs'
alias ke='kubectl exec -it'
alias kaf='kubectl apply -f'
alias kdel='kubectl delete'

kubectl Productivity Tips¶

1. Resource Type Shortcuts¶

# Full name        Short name
pods            ->  po
services        ->  svc
deployments     ->  deploy
replicasets     ->  rs
namespaces      ->  ns
nodes           ->  no
persistentvolumeclaims -> pvc
configmaps      ->  cm
secrets         ->  secret

Example:

kubectl get po
kubectl get svc
kubectl get deploy

2. Watch Mode¶

# Watch resources update in real-time
kubectl get pods -w

# Watch with timestamp
watch kubectl get pods

3. JSONPath Queries¶

# Extract specific fields
kubectl get pods -o jsonpath='{.items[*].metadata.name}'

# Get pod IPs
kubectl get pods -o jsonpath='{.items[*].status.podIP}'

# Complex queries
kubectl get pods -o jsonpath='{range .items[*]}{.metadata.name}{"\t"}{.status.phase}{"\n"}{end}'

# Get resource limits
kubectl get pod nginx -o jsonpath='{.spec.containers[*].resources}'

4. Dry Run¶

# Generate YAML without creating
kubectl create deployment nginx --image=nginx --dry-run=client -o yaml

# Validate manifest
kubectl apply -f app.yaml --dry-run=server

# Generate manifest and apply
kubectl create deployment nginx --image=nginx --dry-run=client -o yaml | kubectl apply -f -

5. Explain Resources¶

# View resource documentation
kubectl explain pod
kubectl explain pod.spec
kubectl explain pod.spec.containers
kubectl explain deployment.spec.strategy

# Show all fields
kubectl explain deployment --recursive

k9s - Terminal UI for Kubernetes¶

k9s provides a terminal-based UI for managing and monitoring Kubernetes clusters.

Launch k9s¶

k9s

# Specific namespace
k9s -n development

# Read-only mode
k9s --readonly

# Different context
k9s --context kind-kind

Key	Action
`:pods` or `:po`	View pods
`:svc`	View services
`:deploy`	View deployments
`:ns`	View namespaces
`0`	Show all namespaces
`1-9`	Switch namespace
`/`	Filter resources
`esc`	Clear filter/back
`?`	Help
`:q` or `Ctrl+C`	Quit

k9s Pod Operations¶

When viewing pods:

Key	Action
`enter`	View pod details
`l`	View pod logs
`s`	Shell into pod
`d`	Describe pod
`e`	Edit pod
`y`	View YAML
`ctrl+k`	Delete pod
`p`	Previous logs
`f`	Port forward

k9s Log Viewing¶

While viewing logs:

Key	Action
`f`	Toggle follow mode
`t`	Toggle timestamp
`w`	Toggle wrap
`s`	Save logs to file
`/`	Search in logs
`n/N`	Next/previous match
`c`	Clear logs

k9s Pulses (Live View)¶

k9s shows live metrics:

CPU and memory usage (if metrics-server installed)
Pod status changes
Events in real-time

k9s Skins and Themes¶

# Change skin (in k9s)
:skin <skin-name>

# Available skins: default, dracula, monokai, nord, etc.

k9s Configuration¶

Config file: ~/.k9s/config.yml

k9s:
  refreshRate: 2
  maxConnRetry: 5
  readOnly: false
  noExitOnCtrlC: false
  ui:
    enableMouse: false
    headless: false
    logoless: false
    crumbsless: false
    skin: dracula
  skipLatestRevCheck: false
  logger:
    sinceSeconds: 300

Troubleshooting Common Issues¶

Pod Not Starting¶

# Check pod status
kubectl get pods

# Describe for events
kubectl describe pod <pod-name>

# Check logs
kubectl logs <pod-name>
kubectl logs <pod-name> --previous  # Previous container

# Common issues:
# - ImagePullBackOff: Wrong image name, no credentials
# - CrashLoopBackOff: Application crashes on startup
# - Pending: Insufficient resources, PVC not bound
# - CreateContainerConfigError: ConfigMap/Secret missing

Service Not Accessible¶

# Verify service exists
kubectl get svc

# Check endpoints (pod IPs)
kubectl get endpoints <service-name>

# Verify labels match
kubectl get pods --show-labels
kubectl describe service <service-name>  # Check selector

# Test from another pod
kubectl run test --image=busybox --rm -it -- wget -O- http://<service>

# Check service type
kubectl get svc <service-name> -o jsonpath='{.spec.type}'

Debugging Network Issues¶

# DNS resolution
kubectl run test --image=busybox --rm -it -- nslookup kubernetes.default

# Connectivity test
kubectl run test --image=nicolaka/netshoot --rm -it -- bash
# Then: ping, curl, dig, traceroute, etc.

# Check CoreDNS
kubectl get pods -n kube-system -l k8s-app=kube-dns
kubectl logs -n kube-system -l k8s-app=kube-dns

Resource Constraints¶

# Check node resources
kubectl top nodes
kubectl describe node <node-name>

# Check pod resources
kubectl top pods
kubectl top pods --containers

# Check resource quotas
kubectl describe resourcequota -n <namespace>

# Check limit ranges
kubectl describe limitrange -n <namespace>

Deployment Rollout Issues¶

# Check rollout status
kubectl rollout status deployment/<name>

# View rollout history
kubectl rollout history deployment/<name>

# View specific revision
kubectl rollout history deployment/<name> --revision=2

# Rollback
kubectl rollout undo deployment/<name>
kubectl rollout undo deployment/<name> --to-revision=2

# Pause/resume rollout
kubectl rollout pause deployment/<name>
kubectl rollout resume deployment/<name>

kubectl Debug Commands¶

# Debug pod (creates ephemeral container)
kubectl debug pod/nginx -it --image=busybox

# Debug node (creates privileged pod on node)
kubectl debug node/kind-worker -it --image=ubuntu

# Copy pod for debugging
kubectl debug pod/nginx --copy-to=nginx-debug --container=nginx -- sh

# Attach to running container
kubectl attach nginx -it

Best Practices¶

Use namespaces: Organize resources logically
Label everything: Makes filtering and selection easier
Use describe: First stop for troubleshooting
Check events: Often reveals the root cause
Use --dry-run: Preview changes before applying
Use contexts: Switch between clusters easily
Enable completion: Save typing and prevent errors
Learn JSONPath: Extract exactly what you need
Use k9s: Faster for exploration and monitoring
Keep cheatsheets handy: Reference common commands

Quick Reference¶

See the kubectl Cheatsheet and k9s Shortcuts for complete references.

Key takeaways¶

kubectl is your primary interface to Kubernetes
describe and logs are essential for troubleshooting
k9s provides a faster, more visual way to manage clusters
Labels and selectors make resource management easier
Contexts let you work with multiple clusters
Dry-run and explain help understand and validate configurations

Check your understanding¶

What's the difference between kubectl create and kubectl apply?
How do you view logs from a previous container instance?
What's the purpose of kubectl describe vs kubectl get?
How do you access a ClusterIP service from your local machine?
What are the advantages of using k9s over kubectl?

Solution

create fails if the resource already exists; apply creates or updates and is idempotent
kubectl logs <pod> --previous
get gives a brief overview; describe gives full details, conditions, and crucially the Events section for debugging
Use kubectl port-forward service/<name> <local-port>:<service-port>
k9s is faster for browsing resources, real-time log tailing, and navigating multiple resource types without typing commands

Hands-on¶

Apply the concepts from this section in the lab exercises.

Next section¶

Once you've reviewed the content and completed the lab, proceed to the next section