What is Kubernetes - Hands-On Activity

What is Kubernetes

📖 Scenario: Imagine you have many small toy robots that need to work together to build a big castle. You want to control them easily, make sure they keep working even if one breaks, and add more robots when needed. Kubernetes helps you do this but with computer programs instead of robots.

🎯 Goal: Learn the basic idea of Kubernetes by creating a simple setup that shows how it manages containers (small packages of software) to keep applications running smoothly.

📋 What You'll Learn

Create a YAML file that defines a Kubernetes Pod with one container

Add a label to the Pod for identification

Use a simple container image like nginx

Display the Pod configuration

💡 Why This Matters

🌍 Real World

Kubernetes helps companies run many software containers reliably, like managing many robots working together.

💼 Career

Understanding Kubernetes basics is essential for DevOps roles that manage cloud applications and infrastructure.

1

Create a basic Pod definition

Create a YAML file called pod.yaml with a Kubernetes Pod definition. The Pod should have apiVersion set to v1, kind set to Pod, and metadata with name set to my-first-pod. Under spec, add one container named nginx-container using the image nginx.

Kubernetes

# Your code here

Hint

Start with the basic structure of a Pod YAML file. Use apiVersion, kind, metadata, and spec. Under spec, define one container with the nginx image.

2

Add a label to the Pod

Add a label called app with the value webserver under the metadata section in the pod.yaml file. This label helps identify the Pod.

Kubernetes

apiVersion: v1
kind: Pod
metadata:
  name: my-first-pod
  # Add the label app: webserver below
spec:
  containers:
  - name: nginx-container
    image: nginx

Hint

Under metadata, add a labels section with app: webserver.

3

Explain the Pod's purpose

Write a comment at the top of the pod.yaml file explaining that this Pod runs an nginx web server container.

Kubernetes

# Your comment here
apiVersion: v1
kind: Pod
metadata:
  name: my-first-pod
  labels:
    app: webserver
spec:
  containers:
  - name: nginx-container
    image: nginx

Hint

Start the file with a comment line beginning with # describing the Pod's purpose.

4

Display the Pod configuration

Print the contents of the pod.yaml file to show the complete Pod configuration.

Kubernetes

# Your code here

Hint

Use Python's open and read functions to print the file contents.

Practice

1. What is the main purpose of Kubernetes?

easy

A. To design websites with HTML and CSS

B. To manage and run many copies of programs across multiple computers

C. To write code for mobile applications

D. To create databases for storing data

Solution

1. Step 1: Understand Kubernetes role

   Kubernetes is a tool that helps run many copies of programs on many computers.

2. Step 2: Compare options

   Only To manage and run many copies of programs across multiple computers describes managing programs across computers, which matches Kubernetes' purpose.

3. Final Answer:

   To manage and run many copies of programs across multiple computers -> Option B

4. Quick Check:

   Kubernetes = Manage many program copies [OK]

Hint: Kubernetes manages many program copies on many computers [OK]

Common Mistakes:

• Confusing Kubernetes with programming languages
• Thinking Kubernetes is for website design
• Mixing Kubernetes with database creation

2. Which command is used to interact with Kubernetes from the command line?

easy

A. kubectl

B. docker

C. git

D. npm

Solution

1. Step 1: Identify Kubernetes command-line tool

   The tool to control Kubernetes is called kubectl.

2. Step 2: Check other options

   Docker manages containers, git manages code versions, npm manages JavaScript packages, so they are not correct.

3. Final Answer:

   kubectl -> Option A

4. Quick Check:

   Kubernetes CLI = kubectl [OK]

Hint: Use kubectl to control Kubernetes from terminal [OK]

Common Mistakes:

• Using docker instead of kubectl for Kubernetes
• Confusing git with Kubernetes commands
• Thinking npm controls Kubernetes

3. What happens if a program managed by Kubernetes crashes on one computer?

medium

A. Kubernetes deletes all copies of the program

B. The program stays crashed and Kubernetes does nothing

C. Kubernetes automatically restarts the program on the same or another computer

D. You must manually restart the program yourself

Solution

1. Step 1: Understand Kubernetes fault handling

   Kubernetes watches programs and restarts them automatically if they crash.

2. Step 2: Evaluate options

   Only Kubernetes automatically restarts the program on the same or another computer describes automatic restart, which matches Kubernetes behavior.

3. Final Answer:

   Kubernetes automatically restarts the program on the same or another computer -> Option C

4. Quick Check:

   Kubernetes auto-restarts crashed programs [OK]

Hint: Kubernetes auto-restarts crashed programs [OK]

Common Mistakes:

• Thinking Kubernetes ignores crashed programs
• Believing Kubernetes deletes programs on crash
• Assuming manual restart is always needed

4. You run kubectl get pods but get an error saying "connection refused". What is the likely problem?

medium

A. Kubernetes cluster is not running or unreachable

B. The kubectl command is misspelled

C. Your computer has no internet connection

D. You typed the wrong pod name

Solution

1. Step 1: Analyze error message

   "Connection refused" means kubectl cannot reach the Kubernetes cluster.

2. Step 2: Check options

   Misspelling would cause command not found, no internet is unrelated if cluster is local, wrong pod name gives different error.

3. Final Answer:

   Kubernetes cluster is not running or unreachable -> Option A

4. Quick Check:

   Connection refused = cluster unreachable [OK]

Hint: Connection refused means cluster is down or unreachable [OK]

Common Mistakes:

• Assuming internet is required for local cluster
• Thinking typo causes connection refused
• Confusing pod name errors with connection errors

5. You want to keep a program running with 3 copies at all times using Kubernetes. Which Kubernetes object should you create?

hard

A. Namespace

B. Service

C. ConfigMap

D. Deployment

Solution

1. Step 1: Identify object for managing program copies

   A Deployment manages multiple copies (replicas) of a program and keeps them running.

2. Step 2: Review other objects

   Service exposes programs to network, ConfigMap stores config data, Namespace groups resources, none manage replicas.

3. Final Answer:

   Deployment -> Option D

4. Quick Check:

   Multiple copies managed by Deployment [OK]

Hint: Use Deployment to keep multiple program copies running [OK]

Common Mistakes:

• Confusing Service with Deployment
• Using ConfigMap to manage replicas
• Thinking Namespace controls program copies