Creating custom namespaces in Kubernetes - Quick Revision & Summary

Recall & Review

beginner

What is a Kubernetes namespace?

A Kubernetes namespace is a way to divide cluster resources between multiple users or teams. It helps organize and separate resources inside the same cluster.

beginner

How do you create a custom namespace using kubectl?

You can create a custom namespace by running:
kubectl create namespace your-namespace-name

intermediate

What is the purpose of a namespace YAML file in Kubernetes?

A namespace YAML file defines the namespace as a resource in a declarative way. It can be applied with kubectl to create the namespace.

beginner

Show a simple YAML example to create a namespace called 'dev-team'.

apiVersion: v1
kind: Namespace
metadata:
name: dev-team

beginner

Why use namespaces in Kubernetes?

Namespaces help separate resources for different projects or teams, avoid name conflicts, and apply policies or limits per namespace.

Which command creates a new namespace named 'test-env'?

A kubectl apply namespace test-env

B kubectl new namespace test-env

C kubectl create namespace test-env

D kubectl set namespace test-env

The correct command to create a namespace is 'kubectl create namespace '.

What is the default namespace in Kubernetes if none is specified?

A kube-system

B default

C public

D global

The default namespace is called 'default' where resources go if no namespace is specified.

Which YAML 'kind' is used to define a namespace?

A Namespace

B Pod

C Service

D Deployment

The kind 'Namespace' is used in YAML files to define a namespace resource.

Namespaces in Kubernetes help to:

A Separate cluster resources for different teams

B Increase CPU speed

C Store container images

D Manage network traffic

Namespaces separate resources logically for teams or projects inside the same cluster.

How do you apply a namespace YAML file named 'namespace.yaml'?

A kubectl delete -f namespace.yaml

B kubectl create namespace.yaml

C kubectl run namespace.yaml

D kubectl apply -f namespace.yaml

Use 'kubectl apply -f ' to create or update resources from a YAML file.

Explain how to create a custom namespace in Kubernetes using both command line and YAML file.

Think about both direct commands and declarative YAML approach.

Describe why namespaces are useful in Kubernetes clusters.

Consider how namespaces help manage resources in a shared environment.

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