Labels And Selectors

Labels are like tags which you attach to K8s Objects and helps in identifying their properties (e.g., env: prod, tier: backend)
Selectors are used to select/filter items based on these labels.
Example:
- Add labels like env=prod
- Then run: kubectl get pods --selector env=prod to view only those pods which has env value prod`.
Over time, your cluster may have thousands of objects so labels help group and filter them.

How to Add Labels

Add them in the pod definition file under metadata.labels:
```
metadata:
  labels:
    env: prod
```

Connecting Objects

Kubernetes uses labels and selectors internally to connect objects.

ReplicaSet Example:

In a ReplicaSets YAML, there are two label sections:
1. Top-level labels → for ReplicaSet object itself
2. Inside template.metadata.labels → for the pods it manages
If matches, the labels defined on Pods to decide which ones it should manage

Services Example:

Service also uses selectors to find which Pods to connect to.
It matches the labels defined on Pods to decide which ones it should send traffic to.

Multiple Labels:

If multiple pods share same label (e.g., app=yoda), but do different things,you can use extra labels to make the selector more specific.

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References

https://kubernetes.io/docs/concepts/overview/working-with-objects/labels/