I have one deployment running :

# kubectl get deployments
NAME                   DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE
kubernetes-dashboard   4         4         4            4           131d

I can view the current deployment config using :

# kubectl get deployments kubernetes-dashboard -o yaml
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  annotations:
    deployment.kubernetes.io/revision: "2"
  creationTimestamp: 2017-02-03T16:04:04Z
  generation: 5
  labels:
    app: kubernetes-dashboard
  name: kubernetes-dashboard
  namespace: default
  resourceVersion: "33197158"
  selfLink: /apis/extensions/v1beta1/namespaces/default/deployments/kubernetes-dashboard
  uid: 627d92b2-ea2a-11e6-a152-0050569b714e
spec:
  replicas: 4
  selector:
    matchLabels:
      app: kubernetes-dashboard
  strategy:
    rollingUpdate:
      maxSurge: 1
      maxUnavailable: 1
    type: RollingUpdate
  template:
    metadata:
      annotations:
        scheduler.alpha.kubernetes.io/tolerations: |
          [
            {
              "key": "dedicated",
              "operator": "Equal",
              "value": "master",
              "effect": "NoSchedule"
            }
          ]
      creationTimestamp: null
      labels:
        app: kubernetes-dashboard
    spec:
      containers:
      - args:
        - --apiserver-host=http://172.29.219.6:8080
        image: gcr.io/google_containers/kubernetes-dashboard-amd64:v1.5.0
        imagePullPolicy: Always
        livenessProbe:
          failureThreshold: 3
          httpGet:
            path: /
            port: 9090
            scheme: HTTP
          initialDelaySeconds: 30
          periodSeconds: 10
          successThreshold: 1
          timeoutSeconds: 30
        name: kubernetes-dashboard
        ports:
        - containerPort: 9090
          protocol: TCP
        resources: {}
        terminationMessagePath: /dev/termination-log
      dnsPolicy: ClusterFirst
      restartPolicy: Always
      securityContext: {}
      terminationGracePeriodSeconds: 30
status:
  availableReplicas: 4
  observedGeneration: 5
  replicas: 4
  updatedReplicas: 4

Now I want to edit replicas: 4 on the fly. I know that one way to do it is :

kubectl edit  deployment kubernetes-dashboard

But the above method open up a file that I then need to update manually. This becomes a problem for me since I want to automate editing these deployments using an external tool like a script or Ansible.

I was hoping to use something like this :

kubectl set replicas deployment/kubernetes-dashboard replicas=2

But seems like such a command is not supported. Looks like such a command is only supported for image tag.

Is there any way I can update the replicas OR any other property if a deployment but just issuing a command (without having any editor involved)?