Kubernetes Pt2

In the previous post we used kubectl command lines to deploy. However we can create .yaml configuration files and have kubectl create them that way also

the .yaml file will have the following

apiVersion: (name)

kind: Deployment

metadata:

  name: (appName)

  labels:

    app: (imageTag)

spec:

  replicas: (replicaNumber)

  selector:

    matchLabels:

      app: (imageTag)

  template:

    metadata:

      labels:

        app: (imageTag)

    spec:

      containers:

      - name: (imageTag)

        image: (dockerImage)

        ports:

        - containerPort: (portNumber)

Then enter the following command:

kubectl create -f (.yaml file)

I pulled an example from the edx Kubernetes course using the nginx image to deploy a webserver

apiVersion: apps/v1

kind: Deployment

metadata:

  name: webserver

  labels:

    app: nginx

spec:

  replicas: 3

  selector:

    matchLabels:

      app: nginx

  template:

    metadata:

      labels:

        app: nginx

    spec:

      containers:

      - name: nginx

        image: nginx:alpine

        ports:

        - containerPort: 80

This will deploy an app named webserver replicated across three pods.

We can also define a appName-svc-.yaml file to expose our service with the following content:

apiVersion: (get this value from running kubectl api-version)
kind: Service
metadata:
  name: web-service
  labels:
    run: web-service
spec:
  type: (serviceType)
  externalName: (externalLink) *Use this field if serviceType is set to ExternalName
  ports:
  -  port: (portNumber)
     protocol: TCP
  selector:
    app: (imageTag)

Then enter the following command:
kubectl create -f (appName)-svc.yaml

serviceType can be any of the below:

1. LoadBalancer - if the cloud provider Kubernetes is running on provides load balancing.
2. ClusterIP - can only reach the service only from within the cluster
3. NodePort - creates a ClusterIP and NodePort service will route to it. Allows access from outside the cluster by using NodeIP:NodePort
4. ExternalName - maps the service to the contents of the externalName field

Also pulled from the edx Kubernetes course:

apiVersion: v1
kind: Service
metadata:
  name: web-service
  labels:
    run: web-service
spec:
  type: NodePort
  ports:
  -  port: 80
     protocol: TCP
  selector:
    app: nginx