YAML Skeleton (VERY IMPORTANT)

 🚀 Step 1 – First Understand the YAML Skeleton (VERY IMPORTANT)

Almost EVERY Kubernetes YAML looks like this:

apiVersion:
kind:
metadata:
spec:

🧠 Golden Memory Rule

👉 AKMS

A → apiVersion
K → kind
M → metadata
S → spec

If you remember ONLY this → you can reconstruct everything.

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🔹 What goes under each section?

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✅ 1️⃣ apiVersion → "Which API group/version?"

Tells Kubernetes which version of resource API to use

Common values

Resource	apiVersion
Pod	v1
Service	v1
ReplicaSet	apps/v1
Deployment	apps/v1
StatefulSet	apps/v1

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🧠 Memory Tip

👉 Core = v1
👉 Controllers = apps/v1

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✅ 2️⃣ kind → "What are we creating?"

Defines object type

Examples:

kind: Pod
kind: ReplicaSet
kind: Deployment
kind: Service

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🧠 Memory Tip

👉 Just the resource name

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✅ 3️⃣ metadata → "Information ABOUT object"

Used for:

• name

• labels

• namespace

• annotations

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Example

metadata:
  name: myapp
  labels:
    app: paytm

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🧠 Memory Tip

👉 Metadata = Identity of object

(name, labels, namespace)

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✅ 4️⃣ spec → "Actual configuration"

This is the MOST IMPORTANT block

Everything related to:

• replicas

• containers

• image

• ports

• selector

• template

comes under spec

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🧠 Memory Tip

👉 Spec = Behavior/logic

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🔥 Now Understand ReplicaSet Structure

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🧠 How to Think (Process)

Ask:

✔ How many pods? → replicas
✔ Which pods belong to me? → selector
✔ How to create pods? → template
✔ What container? → containers
✔ Which image? → image

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🔹 ReplicaSet Structure Visual Tree

spec
 ├─ replicas
 ├─ selector
 └─ template
      ├─ metadata (labels)
      └─ spec
           └─ containers
                ├─ name
                └─ image

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🔹 Where to write what? (ReplicaSet)

Item	Where to write
labels	metadata + template.metadata
selector	spec.selector
replicas	spec.replicas
containers	template.spec.containers
container name	containers.name
image	containers.image

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🔹 ReplicaSet YAML (Memory Version)

apiVersion: apps/v1
kind: ReplicaSet
metadata:
  name: app
spec:
  replicas: 3
  selector:
    matchLabels:
      app: app
  template:
    metadata:
      labels:
        app: app
    spec:
      containers:
      - name: app
        image: nginx

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🔥 Deployment Structure (VERY EASY)

Deployment = ReplicaSet + updates

So:

👉 Same YAML, just change kind

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🔹 Deployment Tree

spec
 ├─ replicas
 ├─ selector
 ├─ template
 └─ strategy (extra feature)

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🔹 What is extra in Deployment?

Additional features

Feature	Extra field
rolling update	strategy
rollback	rollout history
versioning	revision
scaling	replicas

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🔹 Deployment YAML

apiVersion: apps/v1
kind: Deployment
metadata:
  name: app
spec:
  replicas: 3
  selector:
    matchLabels:
      app: app
  template:
    metadata:
      labels:
        app: app
    spec:
      containers:
      - name: app
        image: nginx:1.0

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🔥 MEMORY TRICKS (Very useful for exams)

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Trick 1 – SAME LABEL TWICE

selector.matchLabels
template.metadata.labels

Must match exactly

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Trick 2 – Just remember this order

👉 Workload formula:

replicas
selector
template
containers
image

That’s 90% YAML

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🔥 BEST PART – Generate YAML automatically (NO manual writing)

YES ✅
You can generate YAML using command.

This is what real DevOps engineers do.

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🔹 Generate Deployment YAML

kubectl create deployment myapp \
  --image=nginx \
  --replicas=3 \
  --dry-run=client -o yaml > deploy.yml

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🔹 Generate ReplicaSet YAML

kubectl create rs myapp \
  --image=nginx \
  --replicas=3 \
  --dry-run=client -o yaml > rs.yml

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🔹 Generate Pod YAML

kubectl run mypod \
  --image=nginx \
  --dry-run=client -o yaml > pod.yml

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🔹 Generate Service YAML

kubectl expose deploy myapp \
  --port=80 \
  --target-port=80 \
  --type=NodePort \
  --dry-run=client -o yaml > svc.yml

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🔥 Why this method is best?

Instead of:
❌ Writing 40 lines manually

Do:
✅ Generate → Edit → Apply

Flow:

kubectl create --dry-run → generate yaml
vim file.yml → edit
kubectl apply -f file.yml

This is industry standard practice 👍

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🔥 Final Super Memory Summary

Just remember:

AKMS

apiVersion
kind
metadata
spec

Workloads

replicas
selector
template
containers
image

Deployment = ReplicaSet + strategy

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🎯 10-Second Brain Hack

If blank in exam:

Write:

Deployment
  → replicas
  → selector
  → template
      → containers
          → image

You’ll reconstruct everything 😄