Label-based filtering with kubectl in Kubernetes - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the command to list pods with the label app=nginx.

Kubernetes

kubectl get pods -l [1]

Drag options to blanks, or click blank then click option'

Aapp=nginx

Bapp-nginx

Capp_nginx

Dapp:nginx

Attempts:

3 left

💡 Hint

Common Mistakes

Using dashes or colons instead of equal sign in label selector.

Missing the -l flag before the label selector.

The correct label selector syntax is key=value. So app=nginx selects pods with label app equal to nginx.

2fill in blank

medium

Complete the command to list services with the label tier=backend.

Kubernetes

kubectl get services --selector=[1]

Drag options to blanks, or click blank then click option'

Atier:backend

Btier-backend

Ctier=backend

Dtier_backend

Attempts:

3 left

💡 Hint

Common Mistakes

Using dashes or underscores instead of equal sign.

Forgetting to use the --selector flag.

The --selector flag uses the same label selector syntax as -l. Use tier=backend to filter services with that label.

3fill in blank

hard

Fix the error in the command to list pods with label environment=prod.

Kubernetes

kubectl get pods -l [1]

Drag options to blanks, or click blank then click option'

Aenvironment=prod

Benvironment-prod

Cenvironment:prod

Denvironment_prod

Attempts:

3 left

💡 Hint

Common Mistakes

Using dash or colon instead of equal sign.

Missing the -l flag.

The correct label selector format is key=value. Using dashes or colons causes errors.

4fill in blank

hard

Fill both blanks to list pods with label app=web and tier=frontend.

Kubernetes

kubectl get pods -l [1],[2]

Drag options to blanks, or click blank then click option'

Aapp=web

Bapp-web

Ctier=frontend

Dtier-frontend

Attempts:

3 left

💡 Hint

Common Mistakes

Using dashes instead of equal signs.

Separating labels with spaces instead of commas.

Multiple labels are separated by commas. Each label uses key=value format.

5fill in blank

hard

Fill all three blanks to list pods with label app=api, environment=staging, and version=v1.

Kubernetes

kubectl get pods -l [1],[2],[3]

Drag options to blanks, or click blank then click option'

Aapp=api

Benvironment=staging

Cversion=v1

Dversion-v1

Attempts:

3 left

💡 Hint

Common Mistakes

Using dashes instead of equal signs.

Missing commas between labels.

Use commas to separate multiple labels. Each label must be in key=value format.

Practice

1. What does the -l option do in the kubectl get command?

easy

A. Filters resources based on their labels

B. Lists all namespaces in the cluster

C. Deletes resources matching a label

D. Updates the labels of a resource

Solution

1. Step 1: Understand the purpose of -l in kubectl get

   The -l option is used to specify a label selector to filter resources.

2. Step 2: Identify what filtering means in this context

   Filtering means showing only resources that have the specified label(s).

3. Final Answer:

   Filters resources based on their labels -> Option A

4. Quick Check:

   -l filters by labels [OK]

Hint: Remember: -l means label filter in kubectl [OK]

Common Mistakes:

• Confusing -l with namespace filtering
• Thinking -l deletes resources
• Assuming -l updates labels

2. Which of the following is the correct syntax to list pods with the label app=frontend?

easy

A. kubectl get pods -l app=frontend

B. kubectl get pods --label app=frontend

C. kubectl get pods -label app=frontend

D. kubectl get pods -filter app=frontend

Solution

1. Step 1: Recall the correct flag for label filtering

   The correct flag is -l or --selector, not --label or -filter.

2. Step 2: Check the syntax for label selector

   The syntax is -l key=value, so -l app=frontend is correct.

3. Final Answer:

   kubectl get pods -l app=frontend -> Option A

4. Quick Check:

   Use -l key=value for label filtering [OK]

Hint: Use -l key=value to filter by label [OK]

Common Mistakes:

• Using incorrect flags like --label or -filter
• Missing the equals sign between key and value
• Using spaces instead of equals sign

3. Given these pods with labels:
pod1: app=frontend, env=prod
pod2: app=frontend, env=dev
pod3: app=backend, env=prod
What is the output of kubectl get pods -l 'app=frontend,env=prod' -o name?

medium

A. pod/pod3

B. pod/pod1

C. pod/pod2

D. pod/pod1
pod/pod2

Solution

1. Step 1: Understand label selector with multiple labels

   The selector app=frontend,env=prod means pods must have both labels with these exact values.

2. Step 2: Match pods with both labels

   pod1 has app=frontend and env=prod, so it matches. pod2 has env=dev, so no. pod3 has app=backend, so no.

3. Final Answer:

   pod/pod1 -> Option B

4. Quick Check:

   Multiple labels require all to match [OK]

Hint: Multiple labels with commas mean AND condition [OK]

Common Mistakes:

• Assuming comma means OR instead of AND
• Ignoring one of the labels in the selector
• Expecting multiple pods when only one matches all labels

4. You run kubectl get pods -l app=frontend env=prod but get an error. What is the mistake?

medium

A. Labels must be quoted

B. Using wrong resource type

C. Missing comma between labels in the selector

D. kubectl does not support multiple labels

Solution

1. Step 1: Analyze the label selector syntax

   The command uses -l app=frontend env=prod without a comma between labels, which is invalid syntax.

2. Step 2: Correct syntax requires comma separation

   Labels must be separated by commas like -l app=frontend,env=prod to work properly.

3. Final Answer:

   Missing comma between labels in the selector -> Option C

4. Quick Check:

   Separate multiple labels with commas [OK]

Hint: Separate multiple labels with commas, no spaces [OK]

Common Mistakes:

• Forgetting commas between multiple labels
• Adding spaces instead of commas
• Quoting labels unnecessarily

5. You want to list all pods that have label app=frontend but exclude those with label env=dev. Which command achieves this?

hard

A. kubectl get pods -l 'app=frontend' -l 'env!=dev'

B. kubectl get pods -l 'app=frontend' --exclude-label env=dev

C. kubectl get pods -l 'app=frontend' | grep -v env=dev

D. kubectl get pods -l 'app=frontend,env!=dev'

Solution

1. Step 1: Understand label selector for exclusion

   To exclude pods with a label, use key!=value syntax inside the selector.

2. Step 2: Combine inclusion and exclusion in one selector

   Use -l 'app=frontend,env!=dev' to include pods with app=frontend and exclude those with env=dev.

3. Final Answer:

   kubectl get pods -l 'app=frontend,env!=dev' -> Option D

4. Quick Check:

   Use key!=value to exclude labels [OK]

Hint: Use key!=value to exclude labels in selector [OK]

Common Mistakes:

• Trying to use non-existent flags like --exclude-label
• Using multiple -l flags instead of one combined selector
• Using grep which is less efficient and error-prone