5-Deployment

 --------------------------------------------------------------------------
Deployment - this creates a replica set, offers rollback, rolling update of pods 

command to create deployments - kubectl create deployment httpd-frontend --image=http:2.4-alpine --dry-run -o yaml > dep.yaml

command to create deployment - kubectl create deployment httpd-frontend --image=http:2.4-alpine
then scale using command - kubectl scale deployment --replicas=3 httpd-frontend 

 example yaml to create repliaction set (cat > deploy-defintion.yaml)
 
apiVersion: apps/v1
kind: Deployment
metadata:
   name:rc-deployment(this is name of deployment)
   labels:
      app: my-app
      costCenter: US
      
spec:
   template:
      metadata:
         name:nginx-app(this is name of pod)
         labels:
            app: my-app
            costcenter: us
            user: hari
      spec:
         containers:
            - name:nginx-container
              image:nginx
              
   replicas: 3 (this is number of replicas)
   selector:
      matchLabels:
         app:my-app
		 
command - kubectl create -f deploy-defintion.yaml
kubectl get deployments
kubectl get replicaset - this will show replica set created by deployment

to see all object created in kubernetes use command - kubectl get all

commands to generate yml file  - https://kubernetes.io/docs/reference/kubectl/conventions/
command to update the image of a deployment - kubectl set image <deployment name> nginx=nginx:1.9.1

ROLLING UPDATES AND ROLLBACKS

to check the rollout status of a deployment use command - kubectl rollout status <deployment name>
to check the history of a rollout of a deployment use command - kubectl rollout history <deployment name>
command to update the image of a deployment - kubectl set image <deployment name> nginx=nginx:1.9.1
command to rollback to older version of deployment - kubectl rollout undo <deployment name>

 --------------------------------------------------------------------------