Deployments

Kubernetes Deployments automate application upgrades, scaling, and self-healing in production environments. They enable rolling updates, controlled rollbacks, and pause/resume capabilities—all without downtime. In this guide, you’ll learn how Deployments manage ReplicaSets and Pods, define a Deployment manifest, and inspect your resources using kubectl.

Why Use a Deployment?

Rolling Updates: Replace pods one by one to avoid service interruption.
Rollbacks: Instantly revert to a previous version if something goes wrong.
Pause & Resume: Apply several changes as a batch and resume when ready.
Declarative Scaling: Increase or decrease replicas in your manifest.

How Deployments Work

A Deployment sits above ReplicaSets and Pods:

Pod: The basic execution unit (one or more containers).
ReplicaSet: Ensures a specified number of pod replicas run at any time.
Deployment: Manages ReplicaSets and orchestrates updates, rollbacks, and scaling.

The image illustrates a Kubernetes deployment structure, showing a deployment with multiple pods and a replica set, along with versioning and control icons.

Resource Comparison

Resource Type	Purpose	Example Command
Pod	Single instance of one or more containers	`kubectl run nginx --image=nginx`
ReplicaSet	Maintains desired pod replicas	`kubectl create -f replicaset-definition.yml`
Deployment	Declarative updates and rollbacks	`kubectl apply -f deployment-definition.yml`

Writing a Deployment Manifest

Create a YAML file (deployment-definition.yml) to declare your desired state:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp-deployment
  labels:
    app: myapp
    type: front-end
spec:
  replicas: 3
  selector:
    matchLabels:
      type: front-end
  template:
    metadata:
      labels:
        app: myapp
        type: front-end
    spec:
      containers:
        - name: nginx-container
          image: nginx:latest
          ports:
            - containerPort: 80

apiVersion: The API group (apps/v1).
kind: Must be Deployment.
metadata: Identifies the Deployment (name and labels).
spec.replicas: Desired number of pods.
spec.selector: Matches labels on pods.
spec.template: Defines the pod spec, just like a ReplicaSet.

Using kubectl apply -f is recommended for idempotent updates. It creates or updates resources based on your manifest.

Deploying and Inspecting Resources

Create or update the Deployment

kubectl apply -f deployment-definition.yml

View Deployments

kubectl get deployments

Example output:

NAME              READY   UP-TO-DATE   AVAILABLE   AGE
myapp-deployment  3/3     3            3           30s

List ReplicaSets
kubectl get rs
Check Pods
kubectl get pods
See All Resources
kubectl get all

If an update fails, rollback immediately:

kubectl rollout undo deployment/myapp-deployment

Next Steps & References

Watch Video

Demo Replica Sets

Demo Deployments

Introduction

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Why Use a Deployment?

How Deployments Work

Resource Comparison

Writing a Deployment Manifest

Deploying and Inspecting Resources

Next Steps & References

Watch Video

​Why Use a Deployment?

​How Deployments Work

​Resource Comparison

​Writing a Deployment Manifest

​Deploying and Inspecting Resources

​Next Steps & References

Watch Video

Why Use a Deployment?

How Deployments Work

Resource Comparison

Writing a Deployment Manifest

Deploying and Inspecting Resources

Next Steps & References