Kubernetes Namespaces

What is a Kubernetes Namespace?

A Namespace in Kubernetes is a way to logically divide cluster resources. It allows different teams or applications to run in isolation within the same cluster.

Think of namespaces like virtual clusters inside a physical cluster.

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Why Use Namespaces?

• Isolation – Separate workloads for different teams/projects.
• Resource Management – Limit CPU/memory per namespace.
• Access Control – Implement RBAC (Role-Based Access Control) at the namespace level.
• Organized Environment – Separate dev, test, prod workloads.

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Default Namespaces in Kubernetes

Run:

kubectl get namespaces

You'll see:

NAME              STATUS   AGE
default           Active   10d
kube-system       Active   10d
kube-public       Active   10d
kube-node-lease   Active   10d

• default

  • Purpose: Used if no namespace is specified.

• kube-system

  • Purpose: Internal Kubernetes components (e.g., kube-dns).

• kube-public

  • Purpose: Public data visible across the cluster.

• kube-node-lease

  • Purpose: Manages node heartbeats.

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Creating a Namespace

Use kubectl:

kubectl create namespace dev

Or using a YAML file:

apiVersion: v1
kind: Namespace
metadata:
  name: dev

Apply it:

kubectl apply -f namespace.yaml

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Deploying Resources in a Namespace

By default, everything is deployed in the default namespace.
To deploy into a specific namespace, add:

metadata:
  namespace: dev

Example Deployment:

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

Apply:

kubectl apply -f my-app.yaml

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Switching Between Namespaces

Set a default namespace:

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

Now all kubectl commands will run in dev.

Check the current namespace:

kubectl config view --minify | grep namespace

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Listing Resources in a Namespace

kubectl get pods --namespace=dev

Or use shorthand:

kubectl get pods -n dev

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How to access resources across all namespaces

To list resources across all namespaces, use the --all-namespaces flag:

kubectl get pods --all-namespaces

How to access resources from one namespace to another

To access resources from one namespace to another, you can specify the namespace in your resource definitions or commands. For example, to access a service in the dev namespace from the default namespace, you would use the fully qualified domain name (FQDN) of the service:

http://my-service.other-namespace.svc.cluster.local

example:

http://cart-service.dev.svc.cluster.local

Deleting a Namespace

kubectl delete namespace dev

This will delete all resources in that namespace.