03-Deployments.md

Deployments

A Deployment provides declarative updates for Pods and ReplicaSets.

How to create a deployment

• Using Create Command:

kubectl create deployment NAME --image=image -- [COMMAND] [args] [options]

ex kubectl create deployment mydep --image=busybox:latest --image=nginx --port=80 --replicas=2 -- date

• Declarative Format:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
  labels:
    app: nginx
spec:
  replicas: 2
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx:1.14.2
        ports:
        - containerPort: 80

In this example

1. .metadata.name (nginx-deployment) is taken up by the replicaSet and pod.
2. .spec.replicaSet shows it will create 2 replica of the pod.
3. The .spec.selector field defines how the created ReplicaSet finds which Pods to manage. In this case, you select a label that is defined in the Pod template (app: nginx).
4. The Pod template's specification, or .template.spec field, indicates that the Pods run one container, nginx.

Now save this as a file and then deploy it using command kubectl apply -f /path/to/deploy.yaml -n <namespace> | (without -n <namespace> it will be deployed in default namespace)

The you can observe the deployment rollout with the command kubectl get dpeloyment|replicaset|pod -n <namespace>