Kubernetes the k8s -lets Understand it and master the commands

👤 SUVANKAR SARKAR • 📅 April 5, 2026 • 👁️ 41 views • 🔄 Updated May 16, 2026

docker kubernetis k8s container selfhostable

Kubernetes the k8s is the modern solution for containerization eveolved from BSD jail, Per-Process Namespaces and mount system from plan9 os, LXC, even the **WSL2 use 9p.** **[Podman](https://podman.io/)**, **[LXC](https://opencontainers.org/)**, **containerd** is not equal to Docker. minikube and microk8s are similar solution but **Kind** is suitable for local testing (fast, Docker-based). The best light weight solution is k3s perfect for Edge deployment that fully supports ARM based system like Raspberry PI. Linux containerization works by leveraging specific features of the **Linux kernel** to run isolated user-space environments (containers) that share the host machine’s kernel. This is distinct from virtual machines (VMs), which each run a full, separate guest operating system and kernel. The core mechanisms that enable this are **namespaces** and **control groups (cgroups)**: **Namespaces:** These provide the *isolation* by partitioning kernel resources to give each container its own isolated view of the system. Each container effectively gets its own: **Process IDs (PID):** Containers only see their own processes, with an independent process tree, rather than all processes on the host. **Network:** Each container has its own network interfaces, IP addresses, and routing tables. **Mount Points:** This provides an isolated view of the file system, making it appear as a self-contained environment using a layered file system (like OverlayFS). **User IDs (UID):** A user namespace allows the root user inside a container to be mapped to an unprivileged user on the host, enhancing security. **Hostname/Domainname (UTS):** Allows each container to have its own hostname and domain name. **Control Groups (cgroups):** These manage and *limit* the resources that a container can consume, ensuring that no single container can monopolize the host’s resources (CPU, memory, disk I/O, network bandwidth) and impact other containers or the host system. How the Process Works When a user runs a container (e.g., using Docker or Podman), the container engine performs several steps: **Image Retrieval:** The engine pulls a **container image** (a read-only template with application code, libraries, and dependencies) from a registry if it’s not already cached locally. **Environment Setup:** A writable layer is added on top of the image layers to allow for changes during runtime. **Isolation and Resource Allocation:** The container runtime uses Linux kernel system calls to create the necessary **namespaces** for the new containerized process and applies **cgroups** limits for resource governance. **Execution:** The containerized application’s start command is executed within this newly isolated and resource-limited environment ## **One-Liner Summary** | | | | --- | --- | | **Cluster** | Whole system | | **Node** | Single server | | **Pod** | Running container(s) | | **Deployment** | App definition + manager | | **Service** | Stable network access | | **ConfigMap** | Configuration | | **Secret** | Sensitive data | | **kubectl** | Command tool | | **Helm** | Package manager | | **Scale** | Add/remove copies | | **Expose** | Make accessible | | **Port-forward** | Local tunnel | | **metrics-server** | kubectl top | ## **Quick Analogy** Restaurant (Cluster) ├── Chefs (Nodes) ├── Dishes (Pods) ├── Menu (Deployment) - defines dish recipe ├── Waiters (Service) - brings dishes to customers ├── Recipes (ConfigMaps) - cooking instructions ├── Secret Sauce (Secrets) - secret ingredients └── Restaurant Manager (kubectl) - runs the place ### **Core Components**: `kube-apiserver` - Kubernetes API server `kube-controller-manager` - Manages controllers `kube-scheduler` - Schedules pods to nodes `etcd` - Cluster database (if run as pods) ### **Network**: `kube-proxy` - Network proxy on each node `core-dns` / `kube-dns` - DNS service for pods CNI plugins (Calico, Flannel, Cilium, etc.) ### **Add-ons**: `metrics-server` - Resource metrics `ingress-nginx` / other ingress controllers Storage provisioners (CSI drivers) ``` #View everything in kube-system kubectl get all -n kube-system #See system pods kubectl get pods -n kube-system #Check system services kubectl get svc -n kube-system #View critical pods kubectl get pods -n kube-system -o wide | grep -E "kube-apiserver|etcd|scheduler" ``` ### **Cluster** **What**: A set of machines (nodes) running Kubernetes **Think**: The entire Kubernetes “data center” **Example**: Your 3 Raspberry Pis + 1 master = 1 cluster ### **Node** **What**: A single machine (VM or physical) in the cluster **Think**: A “worker bee” or “server” **Example**: `kubectl get nodes` → `node-1`, `node-2`, `node-3` ### **Pod** **What**: Smallest deployable unit, contains 1+ containers **Think**: A “logical host” for containers **Example**: Nginx + Redis containers together in one pod **Life**: Ephemeral (born, live, die) ### **Deployment** **What**: Manages pods, handles updates, rollbacks **Think**: “Pod manager” or “application definition” **Example**: `kubectl create deployment nginx --image=nginx` **Does**: Creates/updates pods, scaling, rollbacks ### **Service** **What**: Stable network endpoint for pods **Think**: “Load balancer” or “stable IP/DNS name” **Example**: `kubectl expose deployment nginx --port=80` **Types**: ClusterIP (internal), NodePort, LoadBalancer ### **Config Map** **What**: Stores configuration data as key-value pairs **Think**: “Environment variables file” **Example**: Database URL, feature flags, settings **Not**: For secrets (use Secret for that) ### **Secret** **What**: Stores sensitive data (base64 encoded) **Think**: “Password manager” for Kubernetes **Example**: API keys, passwords, TLS certificates **Warning**: Base64 is NOT encryption! ## **Commands/Tools** ### **kubectl** (kube-control) **What**: Command-line tool for Kubernetes **Think**: “k8s Swiss Army knife” **Example**: `kubectl get pods`, `kubectl apply -f file.yaml` **Helm** **What**: Package manager for Kubernetes **Think**: “apt/yum for Kubernetes” **Example**: `helm install nginx bitnami/nginx` **Chart**: Helm package (like a .deb/.rpm file) ## **Operations** ### **Scale** **What**: Change number of pod replicas **Think**: “Add/remove copies” of your app **Example**: `kubectl scale deployment nginx --replicas=5` **Auto**: Horizontal Pod Autoscaler (HPA) does this automatically ### **Expose** **What**: Make a deployment accessible **Think**: “Open a door” to your app **Example**: `kubectl expose deployment nginx --port=80 --type=LoadBalancer` ### **Port-forward** **What**: Tunnel to a pod/service from local machine **Think**: “SSH port forwarding” for Kubernetes **Example**: `kubectl port-forward pod/nginx 8080:80` ## **Other Important Concepts** ### **Namespace** **What**: Virtual cluster inside a physical cluster **Think**: “Folders” for organizing resources **Example**: `dev`, `staging`, `production` namespaces **Default**: `default`, `kube-system` (system pods) ### **Ingress** **What**: Manages external HTTP/S access **Think**: “NGINX/Apache” for Kubernetes **Example**: Route `app.example.com` → service **Needs**: Ingress Controller (like nginx-ingress) ### **Persistent Volume (PV) / Persistent Volume Claim (PVC)** **What**: Storage that persists across pod restarts **Think**: “External hard drive” for pods **PV**: The actual storage (disk) **PVC**: “Request” for storage by a pod ### **Daemon Set** **What**: Runs one pod per node **Think**: “Node-level service” **Example**: Log collectors, monitoring agents ### **StatefulSet** **What**: For stateful apps (databases) **Think**: “Pods with stable identity/storage” **Example**: MySQL, PostgreSQL, Elasticsearch ### **Job / CronJob** **What**: Run a task once / on schedule **Think**: “crontab” for Kubernetes **Job**: Run once to completion **CronJob**: Run on schedule (like `*/5 * * * *`) **ReplicaSet** **What**: Maintains a stable set of pod replicas **Think**: “Pod replicas manager” (Deployment uses this internally) **You use**: Deployment (which creates ReplicaSet) ### **Label / Selector** **What**: Key-value tags for filtering/grouping **Think**: “Hashtags” for Kubernetes objects **Example**: `app: nginx`, `env: prod` **Selector**: “Find objects with these labels” ## **Horizontal Pod Autoscaler (HPA) and Vertical Pod Autoscaler (VPA).** ### **Key Aspects of Metrics Server:** **Functionality:** It queries Kubelets on each node to fetch metrics, which are then exposed through the Metrics API. **Purpose:** Exclusively designed for autoscaling pipelines and real-time monitoring; it does not store historical data, making it unsuitable for long-term monitoring solutions. **Installation:** While pre-installed on managed services like Azure AKS, it often requires manual installation on Amazon EKS or self-managed clusters using YAML manifests or Helm. **Components:** It relies on the Kubernetes API to track pods and nodes, and caches pod health information. ### **Usage & Limitations:** **Commands:** Used primarily for `kubectl top node` and `kubectl top pod`. **Limitations:** Cannot be used for non-autoscaling purposes and is not a replacement for full monitoring solutions. ### **Basic Cluster Information** ``` # Check kubectl version and connectivity kubectl version kubectl version --client kubectl cluster-info # Get cluster nodes kubectl get nodes kubectl get nodes -o wide # More details # View cluster events kubectl get events ``` ### **Working with Pods** ``` # List pods kubectl get pods kubectl get pods -A # All namespaces kubectl get pods -o wide # More details kubectl get pods -w # Watch mode # Get detailed pod info kubectl describe pod <pod-name> kubectl describe pod <pod-name> -n <namespace> # Pod logs kubectl logs <pod-name> kubectl logs <pod-name> -f # Follow logs kubectl logs <pod-name> -c <container-name> # Multi-container pods # Execute commands in pod kubectl exec <pod-name> -- <command> kubectl exec -it <pod-name> -- /bin/bash # Interactive shell # Delete pod kubectl delete pod <pod-name> ``` ### **Working with Deployments** ``` # List deployments kubectl get deployments kubectl get deploy # Create deployment kubectl create deployment <name> --image=<image> # Scale deployment kubectl scale deployment <name> --replicas=3 # Update deployment (rolling update) kubectl set image deployment/<name> <container>=<new-image> # Rollback deployment kubectl rollout undo deployment/<name> kubectl rollout history deployment/<name> # Check rollout status kubectl rollout status deployment/<name> ``` ### **Services & Networking** ``` # List services kubectl get services kubectl get svc # Expose deployment as service kubectl expose deployment <name> --port=80 --target-port=8080 --type=LoadBalancer # Port forwarding kubectl port-forward <pod-name> 8080:80 kubectl port-forward svc/<service-name> 8080:80 # Get endpoints kubectl get endpoints ``` ### **Config Maps & Secrets** ``` # ConfigMaps kubectl get configmaps kubectl create configmap <name> --from-literal=key=value kubectl create configmap <name> --from-file=path/to/file # Secrets kubectl get secrets kubectl create secret generic <name> --from-literal=password=secret echo -n 'secret' | base64 # For manual secret creation ``` ### **Namespaces** ``` # List namespaces kubectl get namespaces kubectl get ns # Create namespace kubectl create namespace <name> # Switch context namespace kubectl config set-context --current --namespace=<namespace> # Apply commands to specific namespace kubectl get pods -n <namespace> ``` ### **YAML Operations** ``` # Create resources from YAML kubectl apply -f file.yaml kubectl apply -f ./directory/ # Dry run kubectl apply -f file.yaml --dry-run=client # Generate YAML (without creating) kubectl create deployment <name> --image=nginx --dry-run=client -o yaml > deploy.yaml # Edit resource kubectl edit deployment/<name> # Get resource YAML kubectl get pod <pod-name> -o yaml kubectl get deployment <name> -o yaml > output.yaml ``` ### **Debugging & Diagnostics** ``` # Resource usage kubectl get deployment metrics-server -n kube-system #Error from server (NotFound): deployments.apps "metrics-server" not found kubectl apply -f https://github.com/kubernetes-sigs/metrics-server/releases/latest/download/components.yaml KUBE_EDITOR="nano" kubectl edit deployment metrics-server -n kube-system - args: - --kubelet-insecure-tls - --kubelet-preferred-address-types=InternalIP kubectl top nodes kubectl top pods # API resources kubectl api-resources kubectl api-versions # Explain resource fields kubectl explain pod kubectl explain pod.spec.containers # Run temporary pod for debugging kubectl run debug-pod --image=busybox --rm -it --restart=Never -- /bin/sh ``` ### **Context & Configuration** ``` # List contexts kubectl config get-contexts # Switch context kubectl config use-context <context-name> # Current context kubectl config current-context # View config kubectl config view ``` ### **Handy Shortcuts & Aliases** ``` # Common aliases (add to ~/.bashrc or ~/.zshrc) alias k='kubectl' alias kg='kubectl get' alias kd='kubectl describe' alias kgp='kubectl get pods' alias kgn='kubectl get nodes' alias kaf='kubectl apply -f' alias kdf='kubectl delete -f' alias kl='kubectl logs' alias kex='kubectl exec -it' # Enable autocompletion source <(kubectl completion bash) # For bash source <(kubectl completion zsh) # For zsh ``` ## **Workflow Examples** ### **Deploy an app:** ``` kubectl create deployment nginx --image=nginx kubectl expose deployment nginx --port=80 --type=LoadBalancer kubectl get svc nginx ``` ### **Debug a failing pod:** ``` kubectl get pods kubectl describe pod <problem-pod> kubectl logs <problem-pod> kubectl exec -it <problem-pod> -- /bin/sh ``` ### **Update an app:** ``` kubectl set image deployment/myapp app=myapp:v2 kubectl rollout status deployment/myapp kubectl rollout undo deployment/myapp # If something goes wrong ``` ### **Quick Reference Sheet** ``` Create/Update: kubectl apply -f file.yaml Delete: kubectl delete -f file.yaml Watch: kubectl get pods -w Follow logs: kubectl logs -f <pod> Shell access: kubectl exec -it <pod> -- sh Port forward: kubectl port-forward <pod> 8080:80 Get with wide: kubectl get pods -o wide Describe: kubectl describe <resource> <name> ``` ### **Get the Kubeconfig File** ``` nano ~/.kube/config scp [email protected]/etc/kubernetes/admin.conf ~/.kube/config # Set the cluster kubectl config set-cluster kubernetes \ --server=https://192.168.99.37:6443 \ --certificate-authority=ca.crt # Set credentials (you need the cert and key files) kubectl config set-credentials kubernetes-admin \ --client-certificate=admin.crt \ --client-key=admin.key # Set context kubectl config set-context kubernetes-admin@kubernetes \ --cluster=kubernetes \ --user=kubernetes-admin # Use the context kubectl config use-context kubernetes-admin@kubernetes # Test connectivity kubectl cluster-info # Should show: Kubernetes control plane is running at https://192.168.99.37:6443 # Get nodes kubectl get nodes # Get pods (all namespaces) kubectl get pods -A # If you get certificate errors, you can bypass (not recommended for production): kubectl config set-cluster kubernetes \ --server=https://192.168.99.37:6443 \ --insecure-skip-tls-verify=true # Or copy the CA cert properly scp [email protected]:/etc/kubernetes/pki/ca.crt ~/.kube/ # Then reference it in your config # Test network connectivity telnet 192.168.99.37 6443 # Or nc -zv 192.168.99.37 6443 # If blocked, open port on control plane (if you control it) sudo ufw allow 6443/tcp # Or configure firewall rules ``` ### Something i hate to do ``` # AWS EKS aws eks update-kubeconfig --name cluster-name --region region # Google GKE gcloud container clusters get-credentials cluster-name --region region # Azure AKS az aks get-credentials --resource-group group --name cluster ``` ### some TUI ``` For beginners: Kubernetes Dashboard For daily ops: Lens or K9s (depends on preference) For terminals: K9s (TUI master) For desktop: Lens (full-featured) For enterprise: Rancher For visualization: KubeView For modern UI: Headlamp X- Octant (VMware) ```