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Rolling Updates and Rollback

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In this section, we will take a look at rolling updates and rollback in a deployment

Rollout and Versioning in a Deployment

rollv

Rollout commands

You can see the status of the rollout by the below command
```
$ kubectl rollout status deployment/myapp-deployment
```

To see the history and revisions

$ kubectl rollout history deployment/myapp-deployment

rollc

Deployment Strategies

There are 2 types of deployment strategies
1. Recreate
2. RollingUpdate (Default Strategy)

kubectl apply

To update a deployment, edit the deployment and make necessary changes and save it. Then run the below command.

apiVersion: apps/v1
kind: Deployment
metadata:
 name: myapp-deployment
 labels:
  app: nginx
spec:
 template:
   metadata:
     name: myap-pod
     labels:
       app: myapp
       type: front-end
   spec:
    containers:
    - name: nginx-container
      image: nginx:1.7.1
 replicas: 3
 selector:
  matchLabels:
    type: front-end       

$ kubectl apply -f deployment-definition.yaml

Alternate way to update a deployment say for example for updating an image.
```
$ kubectl set image deployment/myapp-deployment nginx=nginx:1.9.1
```

Recreate vs RollingUpdate

rcrl

Upgrades

Rollback

To undo a change

$ kubectl rollout undo deployment/myapp-deployment

kubectl create

To create a deployment

$ kubectl create deployment nginx --image=nginx

Summarize kubectl commands

$ kubectl create -f deployment-definition.yaml
$ kubectl get deployments
$ kubectl apply -f deployment-definition.yaml
$ kubectl set image deployment/myapp-deployment nginx=nginx:1.9.1
$ kubectl rollout status deployment/myapp-deployment
$ kubectl rollout history deployment/myapp-deployment
$ kubectl rollout undo deployment/myapp-deployment

sum

K8s Reference Docs

https://kubernetes.io/docs/concepts/workloads/controllers/deployment
https://kubernetes.io/docs/tasks/run-application/run-stateless-application-deployment