🧩 Kubernetes ReplicaSet Management

A guide to working with ReplicaSets in Kubernetes, including inspection, editing behavior, and configuration examples.

📦 Listing Pods and ReplicaSets

🔹 List Pods in a Namespace

kubectl get pod -n <namespace>

🔹 List ReplicaSets in a Namespace

kubectl get rs -n <namespace>

✏️ Editing a ReplicaSet

You can attempt to edit a ReplicaSet:

kubectl edit rs -n <namespace> <replica-set-name>

⚠️ Note: Editing the image in a ReplicaSet directly will not automatically update existing Pods. This is because ReplicaSets do not perform rolling updates. Pods will only use the new image after the old ones are deleted and new ones are created.

To apply image changes effectively:

Delete existing Pods manually:

kubectl delete pod -l <label-selector> -n <namespace>

Or, use a higher-level controller like a Deployment for image updates and rolling behavior.

🧾 Example ReplicaSet YAML

Below is a minimal and clear ReplicaSet configuration:

apiVersion: apps/v1
kind: ReplicaSet
metadata:
  name: app-1
  namespace: dev
  labels:
    label1: test1
    app.kubernetes.io/label2: test2
spec:
  replicas: 3
  selector:
    matchLabels:
      app.kubernetes.io/label2: test2
  template:
    metadata:
      labels:
        app.kubernetes.io/label2: test2
        os: linux
    spec:
      containers:
        - name: nginx
          image: nginx

✅ Tip: Ensure that the template.metadata.labels matches exactly with spec.selector.matchLabels. This is critical for proper ReplicaSet Pod matching.

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