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Kubernetes

Working with Kubernetes Pods & Deployment

July 26, 2019 comments off

deployment.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: hello-world
  labels:
    app: hello-world
spec:
  replicas: 4
  selector:
    matchLabels:
      app: hello-world
  template:
    metadata:
      labels:
        app: hello-world
    spec:
      containers:
      - name: hello-world
        image: gcr.io/google-samples/hello-app:1.0
        ports:
        - containerPort: 8080

pod.yaml

apiVersion: v1
kind: Pod
metadata:
  name: hello-world
spec:
  containers:
  - name: hello-world
    image: gcr.io/google-samples/hello-app:1.0
#Anatomy of an API Request
#Creating a pod with YAML
kubectl apply -f pod.yaml

#Get a list of our currently running Pods
kubectl get pod hello-world

#We can use the -v option to increase the verbosity of our request.
#Display requested resource URL. Focus on VERB, API Path and Response code
kubectl get pod hello-world -v 6 

#Same output as 6, add HTTP Request Headers. Focus on application type, and User-Agent
kubectl get pod hello-world -v 7 

#Same output as 7, adds Response Headers and truncated Response Body.
kubectl get pod hello-world -v 8 

#Same output as 8, add full Response. Focus on the bottom, look for metadata
kubectl get pod hello-world -v 9 

#Start up a kubectl proxy session, this will authenticate use to the API Server
#Using our local kubeconfig for authentication and settings
kubectl proxy &
curl http://localhost:8001/api/v1/namespaces/default/pods/hello-world | head -n 20

fg
ctrl+c

#Watch, Exec and Log Requests
#A watch on Pods will watch on the resourceVersion on api/v1/namespaces/default/Pods
kubectl get pods --watch -v 6 &

#We can see kubectl keeps the TCP session open with the server...waiting for data.
netstat -plant | grep kubectl

#Delete the pod and we see the updates are written to our stdout. Watch stays, sicne we're watching All Pods in the default namespace.
kubectl delete pods hello-world

#But let's bring our Pod back...because we have more demos.
kubectl apply -f pod.yaml

#And kill off our watch
fg
ctrl+c

#Accessing logs
kubectl logs hello-world
kubectl logs hello-world -v 6

#Start kubectl proxy, we can access the resource URL directly.
kubectl proxy &
curl http://localhost:8001/api/v1/namespaces/default/pods/hello-world/log 

#Kill our kubectl proxy, fg then ctrl+c
fg
ctrl+c

#Authentication failure Demo
cp ~/.kube/config  ~/.kube/config.ORIG

#Make an edit to our username changing user: kubernetes-admin to user: kubernetes-admin1
vi ~/.kube/config

#Try to access our cluster, and we see GET on ./api/v1/namespaces/default/pods?limit=500 returns a 403. Status, failure.
kubectl get pods -v 6

#Let's put our backup kubeconfig back
cp ~/.kube/config.ORIG ~/.kube/config

#Test out access to the API Server
kubectl get pods 

#Missing resources, we can see the response code for this resources is 404...it's Not Found.
kubectl get pods nginx-pod -v 6

#Let's look at creating and deleting a deployment. We see a query for the existence of the deployment, then a 201 OK on the POST to create the deployment
kubectl apply -f deployment.yaml -v 6

#Get a list of the Deployments
kubectl get deployment 

#Clean up when we're finished. we see a DELETE 200OK and a GET 404.
kubectl delete deployment hello-world -v 6
kubectl delete pod hello-world
What is kubernetes pods with example commands
How to use & troubleshoot Kubernetes pods?
Rajesh Kumar
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