Updating ConfigMaps and propagation in Kubernetes - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the command to update a ConfigMap named 'app-config' from a file 'config.yaml'.

Kubernetes

kubectl create configmap app-config --from-file=[1] --dry-run=client -o yaml | kubectl apply -f -

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

Aconfig.json

Bapp.yaml

Cconfig.yaml

Dsettings.conf

Attempts:

3 left

💡 Hint

Common Mistakes

Using a wrong file name or extension.

Forgetting to use --dry-run=client before applying.

The --from-file option specifies the source file for the ConfigMap. Here, 'config.yaml' is the correct file.

2fill in blank

medium

Complete the command to patch a ConfigMap named 'app-config' with a new key 'log_level' set to 'debug'.

Kubernetes

kubectl patch configmap app-config -p '{"data": {"[1]": "debug"}}'

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

Alog_level

Blog-level

Cloglevel

DlogLevel

Attempts:

3 left

💡 Hint

Common Mistakes

Using camelCase or hyphen instead of underscore.

Misspelling the key name.

The key name in the ConfigMap data is 'log_level' exactly as specified.

3fill in blank

hard

Fix the error in the command to reload pods after ConfigMap update by adding the correct annotation key.

Kubernetes

kubectl patch deployment my-app -p '{"spec": {"template": {"metadata": {"annotations": {"[1]": "$(date +%s)"}}}}}'

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

Akubectl.kubernetes.io/restartedAt

Bkubectl.kubernetes.io/restartAt

Ckubectl.kubernetes.io/restart-time

Dkubectl.kubernetes.io/restart

Attempts:

3 left

💡 Hint

Common Mistakes

Misspelling the annotation key.

Using incomplete or incorrect annotation keys.

The correct annotation key to trigger pod restart is kubectl.kubernetes.io/restartedAt.

4fill in blank

hard

Fill both blanks to create a ConfigMap from literal key-value pairs and apply it.

Kubernetes

kubectl create configmap my-config [1]=value1 [2]=value2 --dry-run=client -o yaml | kubectl apply -f -

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

A--from-literal=key1

B--from-literal=key2

C--from-file=key1

D--from-file=key2

Attempts:

3 left

💡 Hint

Common Mistakes

Using --from-file instead of --from-literal.

Combining multiple keys in one option.

Use --from-literal=key1 and --from-literal=key2 to create ConfigMap entries from literal values.

5fill in blank

hard

Fill all three blanks to update a ConfigMap, patch a deployment to restart pods, and verify pods status.

Kubernetes

kubectl create configmap app-config --from-file=[1] --dry-run=client -o yaml | kubectl apply -f - && kubectl patch deployment my-app -p '{"spec": {"template": {"metadata": {"annotations": {"[2]": "$(date +%s)"}}}}}' && kubectl get pods -l app=my-app -o [3]

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

Aconfig.yaml

Bkubectl.kubernetes.io/restartedAt

Cwide

Djson

Attempts:

3 left

💡 Hint

Common Mistakes

Wrong file name.

Incorrect annotation key.

Using 'json' instead of 'wide' for pod output.

Use 'config.yaml' as the source file, the correct annotation key 'kubectl.kubernetes.io/restartedAt' to restart pods, and 'wide' output format to see pod details.

Practice

1. What happens when you update a ConfigMap in Kubernetes without restarting the pods using it?

easy

A. Pods continue using the old ConfigMap values until restarted

B. Pods automatically reload the new ConfigMap values immediately

C. Kubernetes deletes the pods using the old ConfigMap

D. ConfigMap update fails if pods are running

Solution

1. Step 1: Understand ConfigMap behavior on update

   Updating a ConfigMap does not notify or refresh pods automatically.

2. Step 2: Effect on running pods

   Pods keep using the old ConfigMap data until they are restarted or redeployed.

3. Final Answer:

   Pods continue using the old ConfigMap values until restarted -> Option A

4. Quick Check:

   Pods do not auto-refresh ConfigMaps = B [OK]

Hint: Pods need restart to use updated ConfigMaps [OK]

Common Mistakes:

• Assuming pods auto-refresh ConfigMap changes
• Thinking ConfigMaps update triggers pod restart automatically
• Believing ConfigMap updates delete pods

2. Which command correctly updates a ConfigMap named app-config from a file config.yaml?

easy

A. kubectl update configmap app-config --from-file=config.yaml

B. kubectl edit configmap app-config --from-file=config.yaml

C. kubectl replace configmap app-config --from-file=config.yaml

D. kubectl create configmap app-config --from-file=config.yaml --dry-run=client -o yaml | kubectl apply -f -

Solution

1. Step 1: Understand updating ConfigMap from file

   Direct update requires creating new YAML and applying it.

2. Step 2: Use dry-run and apply for update

   Command C creates new ConfigMap YAML from file and applies it, updating existing ConfigMap.

3. Final Answer:

   kubectl create configmap app-config --from-file=config.yaml --dry-run=client -o yaml | kubectl apply -f - -> Option D

4. Quick Check:

   Use create with dry-run + apply to update ConfigMap = C [OK]

Hint: Use create with dry-run and apply to update ConfigMap [OK]

Common Mistakes:

• Using 'kubectl update' which is not a valid command
• Trying to edit ConfigMap with --from-file option
• Using replace without proper YAML input

3. Given a pod using a ConfigMap mounted as a volume, what is the output of cat /etc/config/app.properties inside the pod immediately after updating the ConfigMap but before restarting the pod?

medium

A. Shows the updated content from the ConfigMap

B. Shows the old content from the ConfigMap before update

C. File is empty because ConfigMap is not mounted

D. Command returns an error because ConfigMap changed

Solution

1. Step 1: Understand ConfigMap volume mount behavior

   ConfigMap mounted as volume is projected as files inside pod at start time.

2. Step 2: Effect of ConfigMap update on mounted files

   Files inside pod do not update automatically; they keep old content until pod restart.

3. Final Answer:

   Shows the old content from the ConfigMap before update -> Option B

4. Quick Check:

   Mounted ConfigMap files do not auto-update = A [OK]

Hint: Mounted ConfigMap files update only after pod restart [OK]

Common Mistakes:

• Assuming mounted files auto-refresh on ConfigMap update
• Expecting empty files if ConfigMap changed
• Thinking command errors due to ConfigMap update

4. You updated a ConfigMap but your pods still use old values. Which command fixes this without deleting pods manually?

medium

A. kubectl rollout restart deployment/myapp

B. kubectl delete pod -l app=myapp

C. kubectl apply -f configmap.yaml

D. kubectl configmap refresh myapp

Solution

1. Step 1: Identify how to refresh pods after ConfigMap update

   Pods must restart to load new ConfigMap values.

2. Step 2: Use rollout restart to restart pods gracefully

   Command 'kubectl rollout restart' triggers pod restart without manual deletion.

3. Final Answer:

   kubectl rollout restart deployment/myapp -> Option A

4. Quick Check:

   Use rollout restart to refresh pods = D [OK]

Hint: Use rollout restart to refresh pods after ConfigMap update [OK]

Common Mistakes:

• Deleting pods manually instead of rollout restart
• Expecting apply to restart pods automatically
• Using non-existent commands like configmap refresh

5. You have a deployment using a ConfigMap for environment variables. After updating the ConfigMap, you want all pods to use the new values without downtime. What is the best approach?

hard

A. Update the ConfigMap and wait; pods auto-refresh environment variables

B. Delete all pods manually to force recreation with new ConfigMap

C. Update the ConfigMap and run kubectl rollout restart deployment/myapp

D. Edit each pod to mount the new ConfigMap version

Solution

1. Step 1: Understand environment variable update behavior

   Pods do not auto-refresh environment variables from ConfigMap updates.

2. Step 2: Use rollout restart for zero downtime update

   Rolling restart updates pods one by one, applying new ConfigMap values without downtime.

3. Final Answer:

   Update the ConfigMap and run kubectl rollout restart deployment/myapp -> Option C

4. Quick Check:

   Rollout restart updates pods gracefully = A [OK]

Hint: Use rollout restart for zero downtime ConfigMap update [OK]

Common Mistakes:

• Expecting pods to auto-refresh env vars
• Deleting pods causing downtime
• Editing pods directly which is not recommended