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⚡ kubectl — Kubernetes CLI Power Guide

kubectl is the primary command-line tool to interact with your Kubernetes cluster via the API server.

It lets you create, inspect, modify, and delete Kubernetes resources.

📂 kubeconfig — Cluster Access Credentials

🔐 What is it?

kubectl uses a config file called **kubeconfig** to:

  • Authenticate to the API server
  • Select the current context (cluster + user + namespace)
  • Store certificates, tokens, and endpoint info

📍 Default location:

~/.kube/config

You can override it using:

kubectl --kubeconfig /path/to/other/config ...

Or set an environment variable:

export KUBECONFIG=/path/to/myconfig

🔧 To set up after kubeadm init:

mkdir -p ~/.kube
sudo cp -i /etc/kubernetes/admin.conf ~/.kube/config
sudo chown $(id -u):$(id -g) ~/.kube/config

🧰 Most Frequently Used kubectl Commands

📊 Cluster Info

kubectl cluster-info
kubectl get nodes
kubectl get componentstatuses  # Deprecated but used in older clusters

📦 Pods, Deployments, Services

kubectl get pods
kubectl get pods -A                 # All namespaces
kubectl get pods -n <namespace>
kubectl describe pod <pod-name>

kubectl get deployments
kubectl describe deployment <name>

kubectl get svc
kubectl describe svc <name>

🚀 Creating Resources

kubectl create deployment nginx --image=nginx
kubectl expose deployment nginx --port=80 --type=NodePort

kubectl run busybox --image=busybox -it --rm -- /bin/sh

🔁 Updating and Managing

kubectl edit deployment nginx         # Opens editor to live-edit
kubectl scale deployment nginx --replicas=5
kubectl rollout restart deployment nginx
kubectl rollout status deployment nginx
kubectl set image deployment/nginx nginx=nginx:1.21

🗑 Deleting Resources

kubectl delete pod <name>
kubectl delete deployment <name>
kubectl delete svc <name>
kubectl delete -f <file>.yaml

🧩 Working with YAML (Declarative Style)

kubectl apply -f deployment.yaml
kubectl get -f deployment.yaml
kubectl delete -f deployment.yaml

📄 Output Formatting

kubectl get pods -o wide
kubectl get pod <name> -o yaml
kubectl get pod <name> -o json
kubectl get pod <name> -o jsonpath='{.status.podIP}'
kubectl get pods -w            # Watch for changes

🐚 Exec and Logs

kubectl exec -it <pod> -- /bin/sh
kubectl exec -it <pod> -c <container> -- /bin/bash

kubectl logs <pod>
kubectl logs <pod> -c <container>
kubectl logs -f <pod>          # Tail logs

📦 Namespaces

kubectl get namespaces
kubectl get pods -n <namespace>
kubectl create namespace dev
kubectl delete namespace dev

kubectl config set-context --current --namespace=dev

🌐 Port Forward and Proxy

kubectl port-forward svc/nginx 8080:80
kubectl port-forward pod/<pod-name> 9090:8080
kubectl proxy

📁 Context & Config Management

kubectl config get-contexts
kubectl config use-context <name>
kubectl config view
kubectl config current-context
kubectl config set-context --current --namespace=dev

⚙️ Dry Runs, Validation, Explain

kubectl apply -f deployment.yaml --dry-run=client
kubectl apply -f deployment.yaml --dry-run=server

kubectl explain pod
kubectl explain deployment.spec.template.spec.containers

🔐 Accessing Secure Clusters

kubectl --token=<jwt> --server=https://<api-server> ...
kubectl --kubeconfig=/path/to/kubeconfig get nodes

📋 Summary Table

Task Command
Get cluster info kubectl cluster-info
List pods kubectl get pods
Create deployment kubectl create deployment
Apply config kubectl apply -f file.yaml
Exec into pod kubectl exec -it <pod> -- /bin/sh
View logs kubectl logs <pod>
Port forward kubectl port-forward <pod> 8080:80
Change namespace kubectl config set-context --current --namespace=dev

🔀 How to Merge Multiple kubeconfig Files

Kubernetes allows you to merge multiple kubeconfig files into a single view by using the KUBECONFIG environment variable.

🗂️ Example Files:

  • $HOME/.kube/config → default config
  • /tmp/dev-kubeconfig
  • /tmp/prod-kubeconfig

✅ Merge Them Temporarily

KUBECONFIG=$HOME/.kube/config:/tmp/dev-kubeconfig:/tmp/prod-kubeconfig kubectl config view --flatten > /tmp/merged-config

Then move or set it as your default config:

mv /tmp/merged-config ~/.kube/config

🔐 Explanation:

Step Description
KUBECONFIG=a:b:c Specifies multiple config files
kubectl config view Shows merged config
--flatten Combines contexts/clusters/users cleanly
> newfile Outputs to a merged file

🔁 Set It Persistently (Optional)

Add to .bashrc or .zshrc:

export KUBECONFIG=$HOME/.kube/config:/tmp/dev-kubeconfig:/tmp/prod-kubeconfig

🧪 Verify the Merge

kubectl config get-contexts
kubectl config use-context <context-name>

🧠 Tip

Always run --flatten when merging — it inlines all references, so it becomes self-contained and safe to share or move.

✅ Pro Tip: Keep your main ~/.kube/config clean by merging only when needed, or use tools like kubectx to manage multiple contexts easily.

Kubectl Official Reference : kubectl-commands