Namespace in Kubernetes

Introduction

Kubernetes is a powerful container orchestration platform, and as clusters grow in size and complexity, it becomes essential to logically separate resources for different teams, environments, or applications. This is where Namespaces in Kubernetes come into play.

Namespaces provide a mechanism for isolating groups of resources within a single Kubernetes cluster.

What is a Namespace?

A namespace is a way to divide cluster resources between multiple users or teams. It allows you to create multiple virtual clusters within the same physical Kubernetes cluster.

Each namespace is a logical partition and can have its own set of:

Pods
Services
Deployments
ConfigMaps, Secrets
Resource quotas and limits

Why Use Namespaces?

Namespaces are useful when:

You have multiple teams sharing the same cluster
You want to avoid resource conflicts (e.g., two apps using the same service name)
You need to apply resource constraints and access controls
You want to separate different environments (e.g., dev, staging, production)

Default Namespaces in Kubernetes

Kubernetes includes the following namespaces by default:

Namespace	Description
`default`	Used when no other namespace is specified.
`kube-system`	Contains resources created by the Kubernetes system (like kube-dns).
`kube-public`	Mostly reserved for cluster-wide public resources. Visible to all users.
`kube-node-lease`	Stores node heartbeats for determining node availability.

Creating a Namespace

You can create a namespace using a YAML file or the kubectl command line.

Using kubectl:

kubectl create namespace dev

Using YAML:

apiVersion: v1
kind: Namespace
metadata:
  name: dev

Apply the file:

kubectl apply -f namespace.yaml

Using a Namespace

To deploy a resource in a specific namespace, specify the namespace in your YAML or use the --namespace flag.

Example:

kubectl create deployment nginx --image=nginx --namespace=dev

Or in YAML:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx
  namespace: dev
spec:
  replicas: 2
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx

Viewing and Switching Namespaces

List all namespaces:

kubectl get namespaces

Get resources in a namespace:

kubectl get pods --namespace=dev

Set default namespace using context:

kubectl config set-context --current --namespace=dev

Resource Quotas and Limits in Namespaces

Namespaces support resource limits to prevent one team from consuming all cluster resources.

ResourceQuota Example:

apiVersion: v1
kind: ResourceQuota
metadata:
  name: dev-quota
  namespace: dev
spec:
  hard:
    pods: "10"
    requests.cpu: "4"
    requests.memory: "4Gi"
    limits.cpu: "10"
    limits.memory: "10Gi"

Apply the quota:

kubectl apply -f quota.yaml

Deleting a Namespace

Warning: Deleting a namespace deletes all resources in it.

kubectl delete namespace dev