kubectl apply vs create in Kubernetes - Practice Questions

Challenge - 5 Problems

🧠 Conceptual

intermediate

Difference in behavior between kubectl create and kubectl apply

What happens if you run kubectl create on a resource that already exists in the cluster?

A It updates the existing resource with new changes.

B It deletes the old resource and creates a new one.

C It ignores the command and does nothing.

D It throws an error saying the resource already exists.

💡 Hint

Think about whether kubectl create is designed to add new resources or modify existing ones.

kubectl create is used to add new resources. If the resource already exists, it will not update it but instead return an error.

🧠 Conceptual

intermediate

Effect of kubectl apply on existing resources

What does kubectl apply do when the resource already exists in the cluster?

A It deletes the existing resource and creates a new one.

B It throws an error saying the resource already exists.

C It updates the existing resource with the changes from the configuration file.

D It ignores the changes and leaves the resource as is.

💡 Hint

Consider how kubectl apply helps keep resources in sync with configuration files.

kubectl apply updates existing resources by applying the changes from the configuration file, allowing incremental updates.

💻 Command Output

advanced

Output of kubectl create on existing resource

What is the output when you run kubectl create -f pod.yaml if the pod already exists?

Kubernetes

kubectl create -f pod.yaml

A error: pods "mypod" already exists

B pod/mypod created

C pod/mypod configured

D Warning: pod/mypod already exists, skipping creation

💡 Hint

Remember that kubectl create does not update existing resources.

When the resource exists, kubectl create returns an error indicating the resource already exists.

💻 Command Output

advanced

Output of kubectl apply on existing resource

What is the output when you run kubectl apply -f deployment.yaml if the deployment already exists and is updated?

Kubernetes

kubectl apply -f deployment.yaml

A deployment.apps/mydeployment configured

B deployment.apps/mydeployment unchanged

C error: deployment.apps "mydeployment" already exists

D deployment.apps/mydeployment created

💡 Hint

Think about how kubectl apply reports changes.

kubectl apply reports configured when it updates an existing resource.

✅ Best Practice

expert

Choosing between kubectl create and apply in CI/CD pipelines

In a continuous deployment pipeline, which command is best to use to ensure the cluster matches the desired state defined in configuration files?

A kubectl get, to verify resources before deployment.

B kubectl apply, because it can create or update resources to match the config files.

C kubectl delete followed by kubectl create, to always start fresh.

D kubectl create, because it ensures resources are only created once.

💡 Hint

Consider which command helps keep resources in sync with config files automatically.

kubectl apply is preferred in CI/CD because it can create new resources or update existing ones, ensuring the cluster matches the desired state.

Practice

1. What is the main difference between kubectl create and kubectl apply?

easy

A. kubectl create only creates new resources and fails if they exist; kubectl apply creates or updates resources.

B. kubectl create updates existing resources; kubectl apply deletes resources.

C. kubectl create deletes resources; kubectl apply only creates new resources.

D. kubectl create and kubectl apply do the same thing.

Solution

1. Step 1: Understand kubectl create behavior

   kubectl create makes new resources but will fail if the resource already exists.

2. Step 2: Understand kubectl apply behavior

   kubectl apply can create new resources or update existing ones safely without failing.

3. Final Answer:

   kubectl create only creates new resources and fails if they exist; kubectl apply creates or updates resources. -> Option A

4. Quick Check:

   create = new only, apply = create or update [OK]

Hint: Create fails if exists; apply updates or creates [OK]

Common Mistakes:

• Thinking create updates existing resources
• Believing apply deletes resources
• Assuming both commands behave identically

2. Which of the following is the correct syntax to create a deployment using kubectl create?

easy

A. kubectl create deployment myapp --image=nginx

B. kubectl create pod myapp --image=nginx

C. kubectl apply deployment myapp --image=nginx

D. kubectl apply -f deployment.yaml

Solution

1. Step 1: Identify kubectl create syntax for deployment

   The command kubectl create deployment myapp --image=nginx creates a deployment named myapp with the nginx image.

2. Step 2: Differentiate from kubectl apply syntax

   kubectl apply uses the -f flag with a file, not direct deployment creation.

3. Final Answer:

   kubectl create deployment myapp --image=nginx -> Option A

4. Quick Check:

   create deployment uses direct command, apply uses files [OK]

Hint: Use 'create deployment' with image flag, apply uses files [OK]

Common Mistakes:

• Using apply syntax with create command
• Mixing file flag with create deployment
• Confusing create and apply commands

3. Given the commands below, what will happen if the deployment myapp already exists?

kubectl create deployment myapp --image=nginx
kubectl apply -f deployment.yaml

medium

A. Both commands will fail because the deployment exists.

B. Both commands will update the deployment.

C. The create command will update; the apply command will fail.

D. The create command will fail; the apply command will update the deployment.

Solution

1. Step 1: Behavior of kubectl create on existing resource

   kubectl create fails if the resource already exists, so the first command will fail.

2. Step 2: Behavior of kubectl apply on existing resource

   kubectl apply updates the existing resource safely, so the second command updates the deployment.

3. Final Answer:

   The create command will fail; the apply command will update the deployment. -> Option D

4. Quick Check:

   create fails if exists; apply updates [OK]

Hint: Create fails if exists; apply updates existing resources [OK]

Common Mistakes:

• Assuming create updates existing resources
• Thinking apply fails if resource exists
• Believing both commands behave the same

4. You ran kubectl create -f service.yaml but got an error saying the service already exists. What should you do to update the service instead?

medium

A. Use kubectl replace -f service.yaml to update the service.

B. Delete the service first, then run kubectl create -f service.yaml again.

C. Use kubectl apply -f service.yaml to update the existing service.

D. Run kubectl create -f service.yaml with a different name.

Solution

1. Step 1: Understand the error cause

   kubectl create fails if the resource exists, so the error means the service is already present.

2. Step 2: Choose the correct update method

   kubectl apply safely updates existing resources without deleting them, so use kubectl apply -f service.yaml.

3. Final Answer:

   Use kubectl apply -f service.yaml to update the existing service. -> Option C

4. Quick Check:

   apply updates existing resources safely [OK]

Hint: Use apply to update existing resources, not create [OK]

Common Mistakes:

• Trying to create again without deleting
• Deleting resources unnecessarily
• Using replace without understanding its effect

5. You want to manage a deployment over time, updating its image and replicas safely without deleting it. Which command should you use and why?

hard

A. Use kubectl create deployment myapp --image=nginx repeatedly to update the deployment.

B. Use kubectl apply -f deployment.yaml because it creates or updates resources safely.

C. Use kubectl delete deployment myapp then kubectl create -f deployment.yaml to update.

D. Use kubectl replace -f deployment.yaml because it creates new resources.

Solution

1. Step 1: Identify the need for safe updates over time

   Managing a deployment means updating it multiple times without deleting or failing.

2. Step 2: Choose the command that supports create or update safely

   kubectl apply can create or update resources safely, preserving existing settings and avoiding errors.

3. Step 3: Evaluate other options

   kubectl create fails if resource exists; deleting is disruptive; replace overwrites but is less safe than apply.

4. Final Answer:

   Use kubectl apply -f deployment.yaml because it creates or updates resources safely. -> Option B

5. Quick Check:

   Manage resources over time with apply [OK]

Hint: Apply manages updates safely; create is one-time only [OK]

Common Mistakes:

• Using create repeatedly causing errors
• Deleting resources unnecessarily
• Confusing replace with apply