Kubernetes Knowledge Transfer Pack

1. Namespaces

Definition: Logical partitions in a cluster, used to separate environments or teams.

Commands:

kubectl get namespaces

kubectl create namespace dev-team

kubectl delete namespace dev-team

2. Pods

Definition: Smallest deployable unit in Kubernetes, wraps one or more containers.

Commands:

kubectl get pods

kubectl get pods --all-namespaces

kubectl describe pod <pod-name>

kubectl delete pod <pod-name>

3. Containers

Definition: Actual running processes inside pods (Docker/containerd images).

Commands:

kubectl logs <pod-name> -c <container-name>

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

4. Deployments

Definition: Controller that manages pods, scaling, and rolling updates.

Commands:

kubectl create deployment nginx-deploy --image=nginx

kubectl scale deployment nginx-deploy --replicas=5

kubectl get deployments

kubectl delete deployment nginx-deploy

5. Services

Definition: Provides stable networking to pods.

Types: ClusterIP, NodePort, LoadBalancer.

Commands:

kubectl expose deployment nginx-deploy --port=80 --target-port=80 --type=ClusterIP

kubectl get svc

kubectl delete svc nginx-deploy

6. ConfigMaps

Definition: Store non‑confidential configuration data.

Commands:

kubectl create configmap app-config --from-literal=ENV=prod

kubectl get configmaps

kubectl describe configmap app-config

7. Secrets

Definition: Store sensitive data (passwords, tokens).

Commands:

kubectl create secret generic db-secret --from-literal=DB_PASSWORD=banking123

kubectl get secrets

kubectl describe secret db-secret

8. Volumes & Storage

Definition: Persistent storage for pods.

Commands:

kubectl get pv

kubectl get pvc --all-namespaces

9. StatefulSets

Definition: Manage stateful apps (databases, Kafka).

Commands:

kubectl apply -f redis-statefulset.yaml

kubectl get statefulsets

10. DaemonSets

Definition: Ensures one pod runs on every node (logging, monitoring).

Commands:

kubectl get daemonsets -n kube-system

11. Jobs & CronJobs

Job: Runs pods until completion.

CronJob: Runs jobs on a schedule.

Commands:

kubectl create job pi --image=perl -- perl -Mbignum=bpi -wle 'print bpi(2000)'

kubectl get jobs

kubectl create cronjob hello --image=busybox --schedule="*/1 * * * *" -- echo "Hello World"

kubectl get cronjobs

12. Ingress

Definition: Manages external HTTP/HTTPS access to services.

Commands:

kubectl apply -f ingress.yaml

kubectl get ingress

🏗 Kubernetes Architecture

Control Plane Components

API Server → Entry point for all requests.

etcd → Cluster state database.

Controller Manager → Ensures desired state.

Scheduler → Assigns pods to nodes.

Node Components

Kubelet → Agent ensuring containers run.

Kube-proxy → Networking rules.

Container Runtime → Runs containers (Docker, containerd).

Add‑ons

CoreDNS → DNS service discovery.

CNI Plugin (Flannel/Calico) → Pod networking.

Metrics Server → Resource monitoring.

📊 Monitoring & Health Commands

kubectl get nodes -o wide

kubectl get pods --all-namespaces -w

kubectl get events --all-namespaces --sort-by=.metadata.creationTimestamp

kubectl top nodes

kubectl top pods

systemctl status kubelet

systemctl status containerd