Deployments Update and Rollback

In Kubernetes, Deployments automate application updates, versioning, and rollbacks. This guide covers:

How rollouts create revisions
Deployment update strategies
Applying and inspecting updates
Undoing changes

Rollouts and Versioning

Whenever you create or modify a Deployment, Kubernetes starts a new rollout, creating a revision:

The image shows a diagram titled "Rollout and Versioning" with two revisions of Nginx versions, 1.7.0 and 1.7.1, represented by icons.

To monitor your rollout and review history:

kubectl rollout status deployment/myapp-deployment
# Waiting for rollout to finish: 0 of 10 updated replicas are available...
# ...
kubectl rollout history deployment/myapp-deployment
# REVISION  CHANGE-CAUSE
# 1         initial create
# 2         updated image to nginx:1.7.1

Use kubectl rollout status to ensure a smooth update before proceeding with any dependent tasks.

Deployment Strategies

Kubernetes supports two primary update strategies:

Recreate

This strategy terminates all existing Pods before creating new ones—resulting in downtime.

The image illustrates a deployment strategy showing a transition from version 1.7.0 to 1.7.1 of nginx, with an application downtime indicated during the process.

Recreate will interrupt service during the update. Use only when downtime is acceptable.

RollingUpdate (default)

With RollingUpdate, old Pods are replaced incrementally, ensuring continuous availability.

The image illustrates two deployment strategies: "Recreate," which results in application downtime, and "Rolling Update," which maintains application availability by updating instances incrementally.

If you omit a strategy in your Deployment spec, RollingUpdate applies by default.

Applying Updates

You can update a Deployment by editing its YAML or using kubectl set image. deployment.yaml:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp-deployment
  labels:
    app: myapp
    tier: frontend
spec:
  replicas: 3
  selector:
    matchLabels:
      app: myapp
      tier: frontend
  template:
    metadata:
      labels:
        app: myapp
        tier: frontend
    spec:
      containers:
        - name: nginx-container
          image: nginx:1.7.0

Apply the manifest:

kubectl apply -f deployment.yaml
# deployment "myapp-deployment" configured

Or update the image directly:

kubectl set image deployment/myapp-deployment \
  nginx-container=nginx:1.9.1
# deployment "myapp-deployment" image updated

Each change creates a new revision and triggers a rollout.

Inspecting Deployment Details

To see strategy settings, ReplicaSet events, and scaling details:

kubectl describe deployment myapp-deployment

Example for Recreate:

Name:                   myapp-deployment
StrategyType:           Recreate
Replicas:               5 desired | 5 total | 5 available
Events:
  Type    Reason             Age   From                   Message
  ----    ------             ----  ----                   -------
  Normal  ScalingReplicaSet  11m   deployment-controller  Scaled up replica set myapp-deployment-6795… to 5

Example for RollingUpdate:

Name:                   myapp-deployment
StrategyType:           RollingUpdate
RollingUpdateStrategy:  25% max unavailable, 25% max surge
Replicas:               5 desired | 6 total | 4 available | 2 unavailable
Events:
  Type    Reason             Age  From                   Message
  ----    ------             ---- ----                   -------
  Normal  ScalingReplicaSet  1m   deployment-controller  Scaled up replica set myapp-deployment-67c7… to 5

Under the hood, each Deployment manages ReplicaSets:

The image is a diagram illustrating a Kubernetes deployment with two replica sets. Replica Set 1 contains five pods, while Replica Set 2 is empty.

List ReplicaSets:

kubectl get replicasets
# NAME                         DESIRED CURRENT READY AGE
# myapp-deployment-67c749c58c  0       0       0     22m
# myapp-deployment-75d7bdbd8d  5       5       5     20m

Rolling Back

To revert a faulty rollout:

kubectl rollout undo deployment/myapp-deployment
# deployment "myapp-deployment" rolled back

After rollback, ReplicaSet counts swap:

kubectl get replicasets
# NAME                         DESIRED CURRENT READY AGE
# myapp-deployment-67c749c58c  5       5       5     22m
# myapp-deployment-75d7bdbd8d  0       0       0     20m

Creating a Deployment with `kubectl run`

Although kubectl run nginx --image=nginx creates a Deployment by default:

kubectl run nginx --image=nginx
# deployment "nginx" created

Using manifest files ensures version control, repeatability, and easier collaboration.

Summary of Key Commands

Command	Description
kubectl create deployment	Create a new Deployment
kubectl get deployments	List Deployments
kubectl apply -f deployment.yaml	Apply or update a Deployment manifest
kubectl set image	Update container image in a Deployment
kubectl rollout status	Monitor rollout progress
kubectl rollout history	View revision history
kubectl rollout undo	Roll back to the previous revision
kubectl describe deployment	Show detailed Deployment settings and events

References

Watch Video

Demo Deployments

Demo Deployments Updates and Rollback

Introduction

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Docker Engine - Security

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Docker Compose

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Disaster Recovery

Deployments Update and Rollback

Rollouts and Versioning

Deployment Strategies

Recreate

RollingUpdate (default)

Applying Updates

Inspecting Deployment Details

Rolling Back

Creating a Deployment with `kubectl run`

Summary of Key Commands

References

Watch Video

​Rollouts and Versioning

​Deployment Strategies

​Recreate

​RollingUpdate (default)

​Applying Updates

​Inspecting Deployment Details

​Rolling Back

​Creating a Deployment with kubectl run

​Summary of Key Commands

​References

Watch Video

Rollouts and Versioning

Deployment Strategies

Recreate

RollingUpdate (default)

Applying Updates

Inspecting Deployment Details

Rolling Back

Creating a Deployment with `kubectl run`

Summary of Key Commands

References