Deployments

In this lesson we cover Kubernetes Deployments — the higher-level API for running applications in production. Deployments manage ReplicaSets, which in turn manage Pods, and provide the following production-ready features:

Multiple instances of a service for availability and load distribution.
Declarative, seamless updates (rolling updates) so not all Pods are replaced at once.
Easy rollbacks to previous revisions when a rollout fails.
Pause/resume support to batch multiple changes (e.g., image update, scaling, resource adjustments) into a single rollout.

Kubernetes Deployments sit above ReplicaSets: a Deployment creates and manages a ReplicaSet, and that ReplicaSet manages Pods. Together they give you declarative updates, controlled rollouts, rollbacks, and pause/resume behavior.

Key configuration points for a Deployment manifest:

spec.replicas — declares how many Pod replicas you want.
spec.selector.matchLabels — must match the labels in spec.template.metadata.labels. This selector tells the Deployment which Pods belong to it and is required for apps/v1 Deployments.

Minimal Deployment manifest example:

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

Create the Deployment:

kubectl create -f deployment-definition.yml
# deployment "myapp-deployment" created

Verify the Deployment, its ReplicaSet, and Pods:

kubectl get deployments
# NAME                READY   UP-TO-DATE   AVAILABLE   AGE
kubectl get replicasets
# NAME                          DESIRED   CURRENT   READY   AGE
kubectl get pods
# NAME                                     READY   STATUS    RESTARTS   AGE
# myapp-deployment-6795844b58-5rbj1        1/1     Running   0          2m
# myapp-deployment-6795844b58-h4w55        1/1     Running   0          2m
# myapp-deployment-6795844b58-lfjhw        1/1     Running   0          2m

Always ensure spec.selector.matchLabels matches the labels on spec.template.metadata.labels. If they don’t match, the Deployment cannot correctly identify and manage its Pods.

To list all objects in the current namespace at once:

kubectl get all
# Lists Deployments, ReplicaSets, Pods, Services, etc., for the namespace

Common Deployment operations and commands:

Operation	Description	Example
Create	Create from a YAML file	`kubectl create -f deployment-definition.yml`
Update image (rolling update)	Update container image, triggers a rollout	`kubectl set image deployment/myapp-deployment nginx-container=nginx:1.21`
Check rollout status	Watch rollout progress	`kubectl rollout status deployment/myapp-deployment`
Rollback	Revert to previous revision	`kubectl rollout undo deployment/myapp-deployment`
Pause/resume rollout	Pause to batch changes, then resume	`kubectl rollout pause deployment/myapp-deployment` `kubectl rollout resume deployment/myapp-deployment`
Scale	Change replica count	`kubectl scale deployment/myapp-deployment --replicas=5`

For more details on strategies and rollout behavior, see the Kubernetes documentation on Deployments and rolling updates:

We will next cover how to perform rolling updates (change the image in the Deployment), how to roll back to previous revisions, and how to pause/resume rollouts to group multiple changes together.

Introduction

Core Concepts

Scheduling

Logging & Monitoring

Application Lifecycle Management

Cluster Maintenance

Security

Storage

Networking

Design and Install a Kubernetes Cluster

Install "Kubernetes the kubeadm way"

Troubleshooting

Helm Basics (2025 Updates)

Kustomize Basics (2025 Updates)

Other Topics

Mock Exams

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