Working with Kubernetes Cluster using Kubectl Part – 6 – Namespaces

namespace.yaml

apiVersion: v1
kind: Namespace
metadata:
  name: playgroundinyaml

deployment.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: hello-world
  labels:
    app: hello-world
  namespace: playground1
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

Commands

ssh aen@c1-master1
cd ~/content/course/m3/demos

#Get a list of all the namespaces in our cluster
kubectl get namespaces

#get a list of all the API resources and if they can be in a namespace
kubectl api-resources --namespaced=true | head
kubectl api-resources --namespaced=false | head

#Namespaces have state, Active and Terminating (when it's deleting)
kubectl describe namespaces

#Describe the details of an indivdual namespace
kubectl describe namespaces kube-system

#Get all the pods in our cluster across all namespaces. Right now, only system pods, no user workload
kubectl get pods --all-namespaces

#Get all the resource across all of our namespaces
kubectl get all --all-namespaces

#Get a list of the pods in the kube-system namespace
kubectl get pods --namespace kube-system

#Imperatively create a namespace
kubectl create namespace playground1

#Imperatively create a namespace...but there's some character restrictions. Lower case and only dashes.
kubectl create namespace Playground1

#Declaratively create a namespace
more namespace.yaml
kubectl apply -f namespace.yaml

#Get a list of all the current namespaces
kubectl get namespaces

#Start a deployment into our playground1 namespace
more deployment.yaml
kubectl apply -f deployment.yaml

#Creating a resource imperitively
kubectl run hello-world-pod \
    --image=gcr.io/google-samples/hello-app:1.0 \
    --generator=run-pod/v1 \
    --namespace playground1

#Where are the pods?
kubectl get pods

#List all the pods on our namespace
kubectl get pods --namespace playground1
kubectl get pods -n playground1

#Get a list of all of the resources in our namespace...Deployment, ReplicaSet and Pods
kubectl get all --namespace=playground1

#Try to delete all the pods in our namespace...this will delete the single pod.
#But the pods under the Deployment controller will be recreated.
kubectl delete pods --all --namespace playground1

#Get a list of all of the *new* pods in our namespace
kubectl get pods -n playground1

#Delete all of the resources in our namespace and the namespace and delete our other created namespace.
#This deletes the Deployment controller, the Pods...or really ALL resources in the namespaces
kubectl delete namespaces playground1
kubectl delete namespaces playgroundinyaml

#List all resources in all namespaces, now our Deployment is gone.
kubectl get all
kubectl get all --all-namespaces

Author
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Rajesh Kumar

DevOps Architect - Mentor - Coach - Trainer at Cotocus

Email - DevOps@RajeshKumar.xyz
CV - www.RajeshKumar.xyz
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Total, Over 15 years of extensive experience working with more than 8 software MNCs for software development/maintenance and production environments involved in continuous improvement and automating entire life cycle using latest devops tools and techniques from design and architecture, through implementation, deployment, and successful operations. Also, helping more than 70 software organizations globally, providing coaching, mentoring and consulting in devops, CICD, cloud, containers and operations.

I help software organization to improve a quality of the software, reducing the software development/operational cost and immediate feedback/monitoring. Have in-depth working experience in following domains with real project implementation.

- Test Driven DevOps Approach
- Continuous Integration
- Continuous Delivery
- Continuous Deployment
- Continuous Inspection
- Technical Debt Reduction
- Containerization/Micro Services Using Kubernetes & Docker
- Cloud Migration using AWS
- Production Monitoring & Postmortem