# Namespaces Walkthrough

Namespaces WalkthroughKubernetes namespaces help different projects, teams, or customers to share a Kubernetes cluster.It does this by providing the following:A scope for Names.A mechanism to attach authorization and policy to a subsection of the cluster.Use of multiple namespaces is optional.This example demonstrates how to use Kubernetes namespaces to subdivide your cluster.Before you beginYou need to have a Kubernetes cluster, and the kubectl command-line tool must be configured to communicate with your cluster. It is recommended to run this tutorial on a cluster with at least two nodes that are not acting as control plane hosts. If you do not already have a cluster, you can create one by using minikube or you can use one of these Kubernetes playgrounds:iximiuz LabsKillercodaKodeKloudPlay with KubernetesTo check the version, enter kubectl version.PrerequisitesThis example assumes the following:You have an existing Kubernetes cluster.You have a basic understanding of Kubernetes Pods, Services, and Deployments.Understand the default namespaceBy default, a Kubernetes cluster will instantiate a default namespace when provisioning the cluster to hold the default set of Pods, Services, and Deployments used by the cluster.Assuming you have a fresh cluster, you can inspect the available namespaces by doing the following:kubectl get namespaces NAME STATUS AGE default Active 13m Create new namespacesFor this exercise, we will create two additional Kubernetes namespaces to hold our content.Let's imagine a scenario where an organization is using a shared Kubernetes cluster for development and production use cases.The development team would like to maintain a space in the cluster where they can get a view on the list of Pods, Services, and Deployments they use to build and run their application. In this space, Kubernetes resources come and go, and the restrictions on who can or cannot modify resources are relaxed to enable agile development.The operations team would like to maintain a space in the cluster where they can enforce strict procedures on who can or cannot manipulate the set of Pods, Services, and Deployments that run the production site.One pattern this organization could follow is to partition the Kubernetes cluster into two namespaces: development and production.Let's create two new namespaces to hold our work.Use the file namespace-dev.yaml which describes a development namespace:admin/namespace-dev.yaml apiVersion: v1 kind: Namespace metadata: name: development labels: name: development Create the development namespace using kubectl.kubectl create -f https://k8s.io/examples/admin/namespace-dev.yaml Save the following contents into file namespace-prod.yaml which describes a production namespace:admin/namespace-prod.yaml apiVersion: v1 kind: Namespace metadata: name: production labels: name: production And then let's create the production namespace using kubectl.kubectl create -f https://k8s.io/examples/admin/namespace-prod.yaml To be sure things are right, let's list all of the namespaces in our cluster.kubectl get namespaces --show-labels NAME STATUS AGE LABELS default Active 32m <none> development Active 29s name=development production Active 23s name=production Create pods in each namespaceA Kubernetes namespace provides the scope for Pods, Services, and Deployments in the cluster.Users interacting with one namespace do not see the content in another namespace.To demonstrate this, let's spin up a simple Deployment and Pods in the development namespace.We first check what is the current context:kubectl config view apiVersion: v1 clusters: - cluster: certificate-authority-data: REDACTED server: https://130.211.122.180 name: lithe-cocoa-92103_kubernetes contexts: - context: cluster: lithe-cocoa-92103_kubernetes user: lithe-cocoa-92103_kubernetes name: lithe-cocoa-92103_kubernetes current-context: lithe-cocoa-92103_kubernetes kind: Config preferences: {} users: - name: lithe-cocoa-92103_kubernetes user: client-certificate-data: REDACTED client-key-data: REDACTED token: 65rZW78y8HbwXXtSXuUw9DbP4FLjHi4b - name: lithe-cocoa-92103_kubernetes-basic-auth user: password: h5M0FtUUIflBSdI7 username: admin kubectl config current-context lithe-cocoa-92103_kubernetes The next step is to define a context for the kubectl client to work in each namespace. The value of "cluster" and "user" fields are copied from the current context.kubectl config set-context dev --namespace=development \ --cluster=lithe-cocoa-92103_kubernetes \ --user=lithe-cocoa-92103_kubernetes kubectl config set-context prod --namespace=production \ --cluster=lithe-cocoa-92103_kubernetes \ --user=lithe-cocoa-92103_kubernetes By default, the above commands add two contexts that are saved into file .kube/config. You can now view the contexts and alternate against the two new request contexts depending on which namespace you wish to work against.To view the new contexts:kubectl config view apiVersion: v1 clusters: - cluster: certificate-authority-data: REDACTED server: https://130.211.122.180 name: lithe-cocoa-92103_kubernetes contexts: - context: cluster: lithe-cocoa-92103_kubernetes user: lithe-cocoa-92103_kubernetes name: lithe-cocoa-92103_kubernetes - context: cluster: lithe-cocoa-92103_kubernetes namespace: development user: lithe-cocoa-92103_kubernetes name: dev - context: cluster: lithe-cocoa-92103_kubernetes namespace: production user: lithe-cocoa-92103_kubernetes name: prod current-context: lithe-cocoa-92103_kubernetes kind: Config preferences: {} users: - name: lithe-cocoa-92103_kubernetes user: client-certificate-data: REDACTED client-key-data: REDACTED token: 65rZW78y8HbwXXtSXuUw9DbP4FLjHi4b - name: lithe-cocoa-92103_kubernetes-basic-auth user: password: h5M0FtUUIflBSdI7 username: admin Let's switch to operate in the development namespace.kubectl config use-context dev You can verify your current context by doing the following:kubectl config current-context dev At this point, all requests we make to the Kubernetes cluster from the command line are scoped to the development namespace.Let's create some contents.admin/snowflake-deployment.yaml apiVersion: apps/v1 kind: Deployment metadata: labels: app: snowflake name: snowflake spec: replicas: 2 selector: matchLabels: app: snowflake template: metadata: labels: app: snowflake spec: containers: - image: registry.k8s.io/serve_hostname imagePullPolicy: Always name: snowflake Apply the manifest to create a Deploymentkubectl apply -f https://k8s.io/examples/admin/snowflake-deployment.yaml We have created a deployment whose replica size is 2 that is running the pod called snowflake with a basic container that serves the hostname.kubectl get deployment NAME READY UP-TO-DATE AVAILABLE AGE snowflake 2/2 2 2 2m kubectl get pods -l app=snowflake NAME READY STATUS RESTARTS AGE snowflake-3968820950-9dgr8 1/1 Running 0 2m snowflake-3968820950-vgc4n 1/1 Running 0 2m And this is great, developers are able to do what they want, and they do not have to worry about affecting content in the production namespace.Let's switch to the production namespace and show how resources in one namespace are hidden from the other.kubectl config use-context prod The production namespace should be empty, and the following commands should return nothing.kubectl get deployment kubectl get pods Production likes to run cattle, so let's create some cattle pods.kubectl create deployment cattle --image=registry.k8s.io/serve_hostname --replicas=5 kubectl get deployment NAME READY UP-TO-DATE AVAILABLE AGE cattle 5/5 5 5 10s kubectl get pods -l app=cattle NAME READY STATUS RESTARTS AGE cattle-2263376956-41xy6 1/1 Running 0 34s cattle-2263376956-kw466 1/1 Running 0 34s cattle-2263376956-n4v97 1/1 Running 0 34s cattle-2263376956-p5p3i 1/1 Running 0 34s cattle-2263376956-sxpth 1/1 Running 0 34s At this point, it should be clear that the resources users create in one namespace are hidden from the other namespace.As the policy support in Kubernetes evolves, we will extend this scenario to show how you can provide different authorization rules for each namespace.