[Solved] Why will this ReplicaSet YAML fail to create pods?apiVersion: apps/v1 kind: ReplicaSet metadata: name: fail-rs spec: replicas: 2 selector: matchLabels: app: fail template: metadata: labels: app:... | Kubernetes

Kubernetes - ReplicaSets and Deployments

Why will this ReplicaSet YAML fail to create pods?

apiVersion: apps/v1
kind: ReplicaSet
metadata:
  name: fail-rs
spec:
  replicas: 2
  selector:
    matchLabels:
      app: fail
  template:
    metadata:
      labels:
        app: frontend
        tier: frontend
    spec:
      containers:
      - name: app
        image: busybox
        command: ["sleep", "3600"]

AThe container image busybox is invalid

BSelector does not match all labels in the pod template

CThe command syntax is incorrect

DThe replicas field must be inside template

Step-by-Step Solution

Solution:

Step 1: Compare selector and pod labels
The selector matches only app: fail, but pod template has app: frontend.
Step 2: Understand label matching rules
The pod template labels must match the selector; mismatched label values cause failure.
Final Answer:
Selector does not match all labels in the pod template -> Option B
Quick Check:
Selector must match pod labels exactly [OK]

Quick Trick: Pod template must have matching labels for selector [OK]

Common Mistakes:

Ignoring label mismatches between selector and pod template
Thinking container image or command is wrong
Misplacing replicas field

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Why will this ReplicaSet YAML fail to create pods?

Step 1: Compare selector and pod labels

Step 2: Understand label matching rules

Final Answer:

Quick Check:

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