This KCNA practice question tests your understanding of kubernetes fundamentals. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
You have a Deployment named 'frontend' with 3 replicas. You want to perform a rolling update to a new container image. Which command should you use?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "which command"
Why it matters: Tests specific CLI syntax. Recall the exact command and its required context — near-synonyms and partial matches are common distractors.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
kubectl set image deployment/frontend container1=nginx:1.20
The `kubectl set image` command is the correct way to perform a rolling update on a Deployment. It directly updates the container image in the pod template, triggering a rolling update where the ReplicaSet gradually replaces old pods with new ones, ensuring zero downtime. Option A specifies the exact container name and new image, which matches the required syntax for a targeted update.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
kubectl set image deployment/frontend container1=nginx:1.20
Why this is correct
This command updates the image for container1 in the frontend deployment.
Clue confirmation
The clue word "which command" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
'kubectl edit' opens the manifest for editing, but the --image flag is not used with it.
✗
kubectl update deployment frontend --image=v2
Why it's wrong here
'kubectl update' is not a valid command.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse imperative commands like `kubectl set image` with declarative commands like `kubectl replace` or non-existent commands like `kubectl update`, leading them to pick options that either require a full manifest or are syntactically invalid.
Trap categories for this question
Command / output trap
'kubectl update' is not a valid command.
Detailed technical explanation
How to think about this question
Under the hood, `kubectl set image` modifies the Deployment's pod template spec, which causes the Deployment controller to create a new ReplicaSet with the updated image and gradually scale down the old ReplicaSet while scaling up the new one, respecting `maxSurge` and `maxUnavailable` settings. This rolling update strategy is the default for Deployments and ensures application availability during the update. In a real-world scenario, if you need to roll back, you can use `kubectl rollout undo deployment/frontend` to revert to the previous ReplicaSet.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the KCNA exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this KCNA question in full detail.
Kubernetes Fundamentals — This question tests Kubernetes Fundamentals — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: kubectl set image deployment/frontend container1=nginx:1.20 — The `kubectl set image` command is the correct way to perform a rolling update on a Deployment. It directly updates the container image in the pod template, triggering a rolling update where the ReplicaSet gradually replaces old pods with new ones, ensuring zero downtime. Option A specifies the exact container name and new image, which matches the required syntax for a targeted update.
What should I do if I get this KCNA question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "which command". Tests specific CLI syntax. Recall the exact command and its required context — near-synonyms and partial matches are common distractors.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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