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Namespaces

Prerequisites

Before using kubectl, please set the KUBECONFIG environment variable to point to the right kubeconfig file.

$ export KUBECONFIG=../02-Multi-node_cluster/vagrant/kubeconfig.yaml

Functionality of Namespace

Namespace provides an additional qualification to a resource name. This is helpful when multiple teams are using the same cluster and there is a potential of name collision. It can be as a virtual wall between multiple clusters.

Following are some of the important functionalities of a Namespace in Kubernetes

  • Namespaces help pod-to-pod communication using the same namespace.
  • Namespaces are virtual clusters that can sit on top of the same physical cluster.
  • They provide logical separation between the teams and their environments.

Create a Namespace

Giving the following yaml called namespace.yaml

apiVersion: v1
kind: Namespace
metadata:
   name: elk

This command is used to create a namespace

$ kubectl create -f namespace.yaml
namespace/elk created

To get all the namespaces

$ kubectl get namespace                                                                                                      
NAME                   STATUS   AGE
default                Active   42m
elk                    Active   28s
kube-node-lease        Active   42m
kube-public            Active   42m
kube-system            Active   42m
kubernetes-dashboard   Active   42m

To get all a single namespace

$ kubectl get namespace elk
NAME   STATUS   AGE
elk    Active   86s

To get namespace informations

$ kubectl describe namespace elk
Name:         elk
Labels:       <none>
Annotations:  <none>
Status:       Active

No resource quota.

No resource limits.

Namespaces can be specified in resource definitions in order to let the resource belong to specific namespace, for example:

apiVersion: v1
kind: Pod
metadata:
  name: memory-demo
  namespace: mem-example
...

or in a Service

apiVersion: v1
kind: Pod
metadata:
  name: memory-demo
  namespace: mem-example
...
$ kubectl create -f pod.yaml  
pod/nginx1 created

To query for pods in a specific namespace

$ kubectl get pods -n elk
NAME     READY   STATUS    RESTARTS   AGE
nginx1   1/1     Running   0          80s

Finally, delete the namespace with all its content (the pod)

$ kubectl delete namespace elk
namespace "elk" deleted