Namespaces Walkthrough

    It does this by providing the following:

    1. A scope for Names.
    2. 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.

    You 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:

    To check the version, enter .

    This example assumes the following:

    1. You have an existing Kubernetes cluster.
    2. You have a basic understanding of Kubernetes , Services, and .

    By 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:

    1. NAME      STATUS    AGE
    2. default   Active    13m

    For 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.

    Use the file namespace-dev.yaml which describes a development namespace:

    1. apiVersion: v1
    2. kind: Namespace
    3. metadata:
    4.   name: development
    5.   labels:
    6.     name: development

    Create the development namespace using kubectl.

    1. 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:

    Namespaces Walkthrough - 图2

    1. apiVersion: v1
    2. kind: Namespace
    3. metadata:
    4.   name: production
    5.   labels:
    6.     name: production

    And then let’s create the production namespace using kubectl.

    1. 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.

    1. kubectl get namespaces --show-labels
    1. NAME          STATUS    AGE       LABELS
    2. default       Active    32m       <none>
    3. development   Active    29s       name=development
    4. production    Active    23s       name=production

    A 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:

    1. kubectl config view
    1. apiVersion: v1
    2. clusters:
    3. - cluster:
    4.     certificate-authority-data: REDACTED
    5.     server: https://130.211.122.180
    6.   name: lithe-cocoa-92103_kubernetes
    7. contexts:
    8. - context:
    9.     cluster: lithe-cocoa-92103_kubernetes
    10.     user: lithe-cocoa-92103_kubernetes
    11.   name: lithe-cocoa-92103_kubernetes
    12. current-context: lithe-cocoa-92103_kubernetes
    13. kind: Config
    14. preferences: {}
    15. - name: lithe-cocoa-92103_kubernetes
    16.   user:
    17.     client-certificate-data: REDACTED
    18.     client-key-data: REDACTED
    20. - name: lithe-cocoa-92103_kubernetes-basic-auth
    21.   user:
    22.     password: h5M0FtUUIflBSdI7
    23.     username: admin
    1. 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.

    1. kubectl config set-context dev --namespace=development \
    2.   --cluster=lithe-cocoa-92103_kubernetes \
    3.   --user=lithe-cocoa-92103_kubernetes
    5. kubectl config set-context prod --namespace=production \
    6.   --cluster=lithe-cocoa-92103_kubernetes \
    7.   --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.

    1. kubectl config view
    1. apiVersion: v1
    2. clusters:
    3. - cluster:
    4.     certificate-authority-data: REDACTED
    5.     server: https://130.211.122.180
    6.   name: lithe-cocoa-92103_kubernetes
    7. contexts:
    8. - context:
    9.     cluster: lithe-cocoa-92103_kubernetes
    10.     user: lithe-cocoa-92103_kubernetes
    11.   name: lithe-cocoa-92103_kubernetes
    12. - context:
    13.     cluster: lithe-cocoa-92103_kubernetes
    14.     namespace: development
    15.     user: lithe-cocoa-92103_kubernetes
    16.   name: dev
    17. - context:
    18.     cluster: lithe-cocoa-92103_kubernetes
    19.     namespace: production
    20.     user: lithe-cocoa-92103_kubernetes
    21.   name: prod
    22. current-context: lithe-cocoa-92103_kubernetes
    23. kind: Config
    24. preferences: {}
    25. users:
    26. - name: lithe-cocoa-92103_kubernetes
    27.   user:
    28.     client-certificate-data: REDACTED
    29.     client-key-data: REDACTED
    30. - name: lithe-cocoa-92103_kubernetes-basic-auth
    31.   user:
    32.     password: h5M0FtUUIflBSdI7
    33.     username: admin

    Let’s switch to operate in the namespace.

    1. kubectl config use-context dev

    You can verify your current context by doing the following:

    1. kubectl config current-context
    1. 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.

    1. apiVersion: apps/v1
    2. kind: Deployment
    3. metadata:
    4.   labels:
    5.     app: snowflake
    6.   name: snowflake
    7. spec:
    8.   replicas: 2
    9.   selector:
    10.     matchLabels:
    11.       app: snowflake
    12.   template:
    13.     metadata:
    14.       labels:
    15.         app: snowflake
    16.     spec:
    17.       containers:
    18.       - image: registry.k8s.io/serve_hostname
    19.         imagePullPolicy: Always
    20.         name: snowflake

    Apply the manifest to create a Deployment

    1. kubectl 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.

    1. NAME         READY   UP-TO-DATE   AVAILABLE   AGE
    2. snowflake    2/2     2            2           2m
    1. kubectl get pods -l app=snowflake
    1. NAME                         READY     STATUS    RESTARTS   AGE
    2. snowflake-3968820950-9dgr8   1/1       Running   0          2m
    3. 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.

    1. kubectl config use-context prod

    The production namespace should be empty, and the following commands should return nothing.

    1. kubectl get deployment
    2. kubectl get pods

    Production likes to run cattle, so let’s create some cattle pods.

    1. kubectl create deployment cattle --image=registry.k8s.io/serve_hostname --replicas=5
    3. kubectl get deployment
    1. NAME         READY   UP-TO-DATE   AVAILABLE   AGE
    2. cattle       5/5     5            5           10s
    1. kubectl get pods -l app=cattle
    1. NAME                      READY     STATUS    RESTARTS   AGE
    2. cattle-2263376956-41xy6   1/1       Running   0          34s
    3. cattle-2263376956-kw466   1/1       Running   0          34s
    4. cattle-2263376956-n4v97   1/1       Running   0          34s
    5. 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.