# Namespaces in Kubernetes

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Published 2022-12-03

This tutorial explains what is and how we can use a namespace in Kubernetes.

You can think of a Namespace as a virtual cluster inside your Kubernetes cluster. You can have multiple namespaces inside a single Kubernetes cluster, and they are all logically isolated from each other.

The namespaces are helpful when different teams or projects share a Kubernetes cluster. Any number of namespaces are supported within a cluster, each logically separated from others but with the ability to communicate with each other.

Info

Namespaces cannot be nested within each other.

The namespaces can be created in 2 ways:

using imperative approach (kubectl create command)
using declarative approach (kubectl apply command)

Using imperative approach, we can run a command like this:

kubectl create namespace my-namespace-1

Using declarative approach, we need to create a yaml file ("my-first-namespace.yaml") as below :

my-first-namespace.yaml
apiVersion: v1
kind: Namespace
metadata:
  name: my-namespace-2
  labels:
    environment: dev
    project: data-moving

and after that we need to run the following command in order to have the namespaces created:

kubectl apply -f my-first-namespace.yaml

If we want to see all the namespaces created so far, we can run the following command:

kubectl get namespaces --show-labels

kubectl get ns --show-labels

The result could be like this:

NAME              STATUS   AGE   LABELS
default           Active   14h   kubernetes.io/metadata.name=default
kube-node-lease   Active   14h   kubernetes.io/metadata.name=kube-node-lease
kube-public       Active   14h   kubernetes.io/metadata.name=kube-public
kube-system       Active   14h   kubernetes.io/metadata.name=kube-system
my-namespace-1    Active   18m   kubernetes.io/metadata.name=my-namespace-1
my-namespace-2    Active   9s    environment=dev,kubernetes.io/metadata.name=my-namespace-2,project=data-moving

Info

Until new namespaces are created, default namespace is used. When the namespace is not specified for a pod, the default namespace will be used.
kube-node-lease namespace holds Lease objects associated with each node. Node leases allow the kubelet to send heartbeats so that the control plane can detect node failure.
kube-public namespace is readable by all clients (including those not authenticated). This namespace is mostly reserved for cluster usage, in case that some resources should be visible and readable publicly throughout the whole cluster.
kube-system namespace is used by the Kubernetes system's objects.

We can obtain more information on a particular namespace using the following command:

kubectl describe ns my-namespace-1

The result could be like this:

Name:         my-namespace-1
Labels:       kubernetes.io/metadata.name=my-namespace-1
Annotations:  <none>
Status:       Active

No resource quota.

No LimitRange resource.

A namespace can be deleted using the following command:

kubectl delete namespace my-namespace-2