Default namespaces overview in Kubernetes - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a namespace in Kubernetes?

A namespace in Kubernetes is like a folder that helps organize and separate resources inside a cluster. It keeps things tidy and avoids conflicts.

beginner

Name the three default namespaces in Kubernetes.

The three default namespaces are: default, kube-system, and kube-public.

beginner

What is the purpose of the default namespace?

The default namespace is where Kubernetes puts your resources if you don't specify any other namespace. It's like the general workspace.

intermediate

What kind of resources are stored in the kube-system namespace?

The kube-system namespace holds system components that run Kubernetes itself, like the scheduler and controller manager. It's for internal cluster tools.

intermediate

Why does Kubernetes have a kube-public namespace?

The kube-public namespace is readable by all users and is used for resources that should be visible to everyone, like cluster info.

Which namespace is used by default when none is specified?

A custom

B kube-system

C kube-public

D default

If you don't specify a namespace, Kubernetes uses the 'default' namespace automatically.

What type of resources are found in the kube-system namespace?

A User applications

B Kubernetes system components

C Public cluster info

D Temporary files

The kube-system namespace contains Kubernetes system components like the scheduler and controller manager.

Which namespace is readable by all users and used for public cluster information?

A kube-public

B default

C kube-system

D admin

The kube-public namespace is readable by all users and holds public cluster information.

If you want to isolate resources for a project, what should you do instead of using default namespaces?

A Use the default namespace

B Delete default namespace

C Create a new namespace

D Use kube-public

Creating a new namespace helps isolate resources for different projects or teams.

Which namespace should you avoid modifying directly because it contains critical system components?

A kube-system

B kube-public

C default

D user

The kube-system namespace contains critical system components and should not be modified directly.

Explain the roles of the three default namespaces in Kubernetes.

Think about who uses each namespace and what kind of resources they hold.

Why is it important to use namespaces in Kubernetes?

Consider how namespaces help keep things tidy and secure.

Practice

1. What is the purpose of namespaces in Kubernetes?

easy

A. To replace pods in the cluster

B. To increase the CPU speed of nodes

C. To organize resources into separate groups within a cluster

D. To store container images

Solution

1. Step 1: Understand what namespaces do

   Namespaces help group and isolate resources in a Kubernetes cluster.

2. Step 2: Identify the correct purpose

   They do not affect CPU speed, store images, or replace pods.

3. Final Answer:

   To organize resources into separate groups within a cluster -> Option C

4. Quick Check:

   Namespaces organize resources [OK]

Hint: Namespaces group resources logically in Kubernetes [OK]

Common Mistakes:

• Thinking namespaces speed up nodes
• Confusing namespaces with image storage
• Believing namespaces replace pods

2. Which of the following is a default namespace in Kubernetes?

easy

A. user-space

B. production

C. development

D. kube-system

Solution

1. Step 1: Recall default namespaces

   Kubernetes provides default namespaces like default, kube-system, and kube-public.

2. Step 2: Identify the correct default namespace

   kube-system is a default namespace for system components, while others are user-defined.

3. Final Answer:

   kube-system -> Option D

4. Quick Check:

   kube-system is default namespace [OK]

Hint: Remember kube-system for system pods [OK]

Common Mistakes:

• Assuming production is default
• Confusing user namespaces with defaults
• Thinking development is built-in

3. What will the command kubectl get pods -n default show?

medium

A. Pods in the default namespace

B. All pods in all namespaces

C. Pods in the kube-system namespace

D. No pods, because default namespace is empty

Solution

1. Step 1: Understand the command syntax

   kubectl get pods -n default lists pods in the namespace named default.

2. Step 2: Identify the namespace targeted

   The -n default flag limits output to the default namespace only.

3. Final Answer:

   Pods in the default namespace -> Option A

4. Quick Check:

   kubectl -n default shows default pods [OK]

Hint: -n specifies namespace for kubectl commands [OK]

Common Mistakes:

• Thinking it shows pods from all namespaces
• Confusing default with kube-system
• Assuming default namespace is always empty

4. You run kubectl get pods but get an error: error: namespace "defaultt" not found. What is the likely cause?

medium

A. Pods do not exist in any namespace

B. The namespace name is misspelled

C. kubectl is not installed

D. The cluster is down

Solution

1. Step 1: Analyze the error message

   The error says namespace "defaultt" not found, indicating a typo.

2. Step 2: Check command usage

   Likely the user typed defaultt instead of default as namespace.

3. Final Answer:

   The namespace name is misspelled -> Option B

4. Quick Check:

   Namespace typo causes not found error [OK]

Hint: Check spelling of namespace names carefully [OK]

Common Mistakes:

• Assuming pods don't exist anywhere
• Blaming kubectl installation
• Thinking cluster is down without checking

5. You want to deploy an app only visible to system components. Which default namespace should you use?

hard

A. kube-system

B. kube-public

C. default

D. custom-namespace

Solution

1. Step 1: Understand namespace roles

   kube-system holds system components and is isolated from normal user apps.

2. Step 2: Choose namespace for system visibility

   Deploying in kube-system makes the app visible only to system components.

3. Final Answer:

   kube-system -> Option A

4. Quick Check:

   System apps use kube-system namespace [OK]

Hint: Use kube-system for system-only apps [OK]

Common Mistakes:

• Using default namespace for system apps
• Choosing kube-public which is for public info
• Using a custom namespace without system access