> ## Documentation Index
> Fetch the complete documentation index at: https://notes.kodekloud.com/llms.txt
> Use this file to discover all available pages before exploring further.
# Deployments Update and Rollback
> This guide covers Kubernetes Deployments, including updates, rollbacks, strategies, and commands for managing application versions.
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:
To monitor your rollout and review history:
```bash theme={null}
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.
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.
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:
```yaml theme={null}
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:
```bash theme={null}
kubectl apply -f deployment.yaml
# deployment "myapp-deployment" configured
```
Or update the image directly:
```bash theme={null}
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:
```bash theme={null}
kubectl describe deployment myapp-deployment
```
Example for **Recreate**:
```plaintext theme={null}
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**:
```plaintext theme={null}
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:
List ReplicaSets:
```bash theme={null}
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:
```bash theme={null}
kubectl rollout undo deployment/myapp-deployment
# deployment "myapp-deployment" rolled back
```
After rollback, ReplicaSet counts swap:
```bash theme={null}
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:
```bash theme={null}
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
* [Kubernetes Basics](https://kubernetes.io/docs/concepts/overview/what-is-kubernetes/)
* [Deployments](https://kubernetes.io/docs/concepts/workloads/controllers/deployment/)
* [kubectl Cheat Sheet](https://kubernetes.io/docs/reference/kubectl/cheatsheet/)