[CKA] 002. Kubernetes Objects

ReplicaSet, Deployment, Services, Namespace, Help Commands

hpyYh
January 14, 2026
2 min read

ReplicaSet

For high availablility

apiVersion: apps/v1
kind: ReplicaSet
metadata:
    name: myapp-replicaset
    labels:
        app: myapp
        type: front-end
spec:
    template:
        metadata:
          name: myapp-pod
          labels:
            app: myapp
            tier: fronted
        spec:
          containers:
            - name: nginx-container
              image: nginx
    replicas: 3
    selector:
        matchLabels:
          tier: fronted

kubectl get rs
kubectl apply -f replicaset.yaml
kubectl scale –replicas=5 rs myapp-replicaset
kubectl edit rs myapp-replicaset

Deployment

deployment > replicaset > pod

apiVersion: apps/v1
kind: Deployment
metadata:
    name: myapp-deployment
    labels:
        app: myapp
        type: front-end
spec:
    replicas: 3
    selector:
        matchLabels:
            app: myapp
            tier: fronted
    template:
        metadata:
            labels:
                app: myapp
                tier: fronted
        spec:
            containers:
                - name: nginx-container
                  image: nginx

useful tip!

kubectl create deployment --image=nginx nginx --replicas=4 --dry-run=client -o yaml > nginx-deployment.yaml

Services

NodePort : external user <-> NodePort <-> pod

apiVersion: v1
kind: Service
metadata:
    name: myapp-nodeport
spec:
    type: NodePort
    ports:
        - port: 80
          nodePort: 30008
    selector:
      app: myapp
      tier: fronted

ClusterIP

apiVersion: v1
kind: Service
metadata:
    name: myapp-nodeport
spec:
    type: ClusterIp
    ports:
        - port: 80
          nodePort: 30008
    selector:
      app: myapp
      tier: fronted

LoadBalancer

apiVersion: v1
kind: Service
metadata:
    name: myapp-nodeport
spec:
    type: LoadBalancer
    ports:
        - port: 80
          nodePort: 30008
    selector:
      app: myapp
      tier: fronted

what endpoint count? : connected pod port count

Namespace

same namesapce connect : service
diff namespace connect : service.namespace.svc.cluster.local
kubectl get pod –namespace=dev (-n=dev)

Help Commands

apply

declarative (not imperative)
create, edit, replace => apply

api-resource

list resource types

explain

object documentation
kubectl explain
kubectl explain .
kubectl explain –recursive

tags :
Cka