Creating custom namespaces in Kubernetes - Step-by-Step CLI Walkthrough

Introduction

When you run many applications in Kubernetes, they can get mixed up and hard to manage. Creating custom namespaces helps keep your apps organized by grouping related resources together.

When you want to separate development and production environments in the same cluster.

When multiple teams share the same Kubernetes cluster and need isolated spaces.

When you want to apply different access controls to different groups of resources.

When you want to limit resource usage for a specific group of applications.

When you want to organize resources by project or application type.

Config File - namespace.yaml

namespace.yaml

apiVersion: v1
kind: Namespace
metadata:
  name: example-namespace

This file defines a new namespace named example-namespace. The apiVersion and kind tell Kubernetes what type of object this is. The metadata.name sets the namespace's name.

Commands

This command creates the custom namespace defined in the namespace.yaml file. It tells Kubernetes to add this new isolated space.

Terminal

kubectl apply -f namespace.yaml

Expected Output

namespace/example-namespace created

This command lists all namespaces in the cluster so you can verify your new namespace was created.

Terminal

kubectl get namespaces

Expected Output

NAME              STATUS   AGE

default           Active   10d

kube-system       Active   10d

example-namespace  Active   1m

This command sets your current kubectl context to use the new namespace by default, so you don't have to specify it in every command.

Terminal

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

Expected Output

Context "your-cluster-context" modified.

This command lists pods in the current namespace, which is now example-namespace. It helps confirm you are working inside the right namespace.

Terminal

kubectl get pods

Expected Output

No resources found in example-namespace namespace.

Key Concept

If you remember nothing else from this pattern, remember: namespaces create isolated spaces in Kubernetes to organize and separate resources.

Common Mistakes

Not creating a namespace before trying to deploy resources into it.

Kubernetes will fail to find the namespace and the deployment will not work.

Always create the namespace first using a YAML file or kubectl before deploying resources there.

Forgetting to switch the kubectl context to the new namespace.

kubectl commands will run in the default namespace, causing confusion or resource deployment in the wrong place.

Use 'kubectl config set-context --current --namespace=your-namespace' to switch namespaces.

Summary

Create a namespace YAML file to define a new isolated space.

Apply the YAML file with kubectl to create the namespace.

List namespaces to verify creation.

Set your kubectl context to the new namespace for easier management.

Practice

1. What is the main purpose of creating a custom namespace in Kubernetes?

easy

A. To increase the number of nodes in the cluster

B. To group and isolate resources for better organization

C. To speed up container image downloads

D. To automatically update all pods

Solution

1. Step 1: Understand Kubernetes namespaces

   Namespaces help organize and isolate resources within the same cluster.

2. Step 2: Identify the purpose of custom namespaces

   Custom namespaces separate projects, teams, or environments for clarity and management.

3. Final Answer:

   To group and isolate resources for better organization -> Option B

4. Quick Check:

   Namespaces = Organize resources [OK]

Hint: Namespaces isolate resources logically, not physically [OK]

Common Mistakes:

• Thinking namespaces add nodes
• Confusing namespaces with pods
• Believing namespaces speed up downloads

2. Which YAML snippet correctly defines a custom namespace named dev-team?

easy

A. apiVersion: v1\nkind: Namespace\nmetadata:\n name: dev-team

B. apiVersion: v1\nkind: Pod\nmetadata:\n name: dev-team

C. apiVersion: apps/v1\nkind: Namespace\nmetadata:\n name: dev-team

D. apiVersion: v1\nkind: Service\nmetadata:\n name: dev-team

Solution

1. Step 1: Identify correct apiVersion and kind for namespace

   The correct apiVersion is 'v1' and kind is 'Namespace' for creating namespaces.

2. Step 2: Check metadata name field

   The metadata name must be the desired namespace name, here 'dev-team'.

3. Final Answer:

   apiVersion: v1\nkind: Namespace\nmetadata:\n name: dev-team -> Option A

4. Quick Check:

   Namespace YAML = apiVersion v1 + kind Namespace [OK]

Hint: Namespace kind is always 'Namespace' with apiVersion 'v1' [OK]

Common Mistakes:

• Using wrong kind like Pod or Service
• Using wrong apiVersion like apps/v1
• Missing metadata name field

3. What will be the output of the command kubectl get namespaces after applying this YAML?

apiVersion: v1
kind: Namespace
metadata:
  name: test-env

medium

A. Only default namespaces are shown, 'test-env' is missing

B. Shows an error: namespace 'test-env' already exists

C. No output, command hangs

D. Lists all namespaces including 'test-env'

Solution

1. Step 1: Apply the namespace YAML

   Applying the YAML creates a new namespace named 'test-env' in the cluster.

2. Step 2: Run 'kubectl get namespaces'

   This command lists all namespaces, including the newly created 'test-env'.

3. Final Answer:

   Lists all namespaces including 'test-env' -> Option D

4. Quick Check:

   kubectl get namespaces shows all namespaces [OK]

Hint: New namespaces appear in 'kubectl get namespaces' output [OK]

Common Mistakes:

• Expecting error if namespace exists (it won't if new)
• Thinking command hangs
• Assuming only default namespaces show

4. You tried to create a namespace with this YAML but got an error:

apiVersion: v1
kind: Namespace
metadata:
  name: 123team

What is the likely cause?

medium

A. Namespace names cannot start with a number

B. apiVersion 'v1' is incorrect for namespaces

C. Missing 'labels' field in metadata

D. Namespace kind should be 'Project'

Solution

1. Step 1: Check namespace naming rules

   Namespace names must start with a letter and contain only lowercase letters, numbers, and dashes.

2. Step 2: Identify invalid name

   The name '123team' starts with a number, which is invalid and causes the error.

3. Final Answer:

   Namespace names cannot start with a number -> Option A

4. Quick Check:

   Namespace name rules forbid starting with digits [OK]

Hint: Namespace names must start with a letter, not a number [OK]

Common Mistakes:

• Thinking apiVersion v1 is wrong
• Believing labels are mandatory
• Using wrong kind like 'Project'

5. You want to create two namespaces, dev and prod, and ensure pods in dev cannot access services in prod. Which approach is best?

hard

A. Create namespaces and use different node pools for each

B. Create namespaces and label pods with 'access=restricted' only

C. Create both namespaces and use NetworkPolicies to restrict access

D. Create namespaces and deploy all pods in the default namespace

Solution

1. Step 1: Create separate namespaces

   Namespaces 'dev' and 'prod' isolate resources logically in the cluster.

2. Step 2: Use NetworkPolicies to control traffic

   NetworkPolicies can restrict pod-to-service communication between namespaces effectively.

3. Final Answer:

   Create both namespaces and use NetworkPolicies to restrict access -> Option C

4. Quick Check:

   Namespaces + NetworkPolicies = access control [OK]

Hint: Use NetworkPolicies with namespaces for access control [OK]

Common Mistakes:

• Assuming labels alone restrict network access
• Deploying all pods in default namespace ignores isolation
• Using node pools does not isolate network traffic