This CKS practice question tests your understanding of cluster setup and hardening. 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.
A pod running in the cluster is in a CrashLoopBackOff state. You run 'kubectl describe pod <pod>' and see the following event: 'Warning BackOff Back-off restarting failed container'. Which command would you run to see the standard error output of the container?
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 logs <pod> --previous
Option A is correct because `kubectl logs <pod> --previous` retrieves the logs from the previous instance of a crashed or restarting container. When a pod is in CrashLoopBackOff, the current container may have already restarted, so the standard error output from the failed run is only available in the previous container's logs. This command specifically fetches those logs, which typically contain the stderr output that caused the crash.
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 logs <pod> --previous
Why this is correct
Using --previous retrieves logs from the previous instance of the container, which is essential when the container is restarting due to a crash.
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 exec <pod> -- cat /var/log/syslog
Why it's wrong here
The pod may be crashed and exec may not work; also the log location is not standard.
✗
kubectl describe pod <pod>
Why it's wrong here
This provides events and configuration but does not show the container's standard error output.
✗
kubectl logs <pod>
Why it's wrong here
This shows the current container's logs, which may be empty if the container just started and crashed.
Common exam traps
Common exam trap: answer the scenario, not the keyword
CNCF often tests the distinction between `kubectl logs <pod>` and `kubectl logs <pod> --previous`; the trap here is that candidates assume the current container's logs contain the crash information, but in a CrashLoopBackOff, the current container may have already restarted and its logs are empty or show only the restart loop, so the `--previous` flag is required to see the actual error output from the failed run.
Trap categories for this question
Command / output trap
This provides events and configuration but does not show the container's standard error output.
Detailed technical explanation
How to think about this question
Under the hood, when a container exits with a non-zero exit code, the kubelet records the container's termination log (including stderr) and increments the restart count. The `--previous` flag instructs the kubelet to return logs from the terminated container instance, which is stored in the container's log file on the node (typically under /var/log/pods/). In real-world scenarios, this is critical for debugging init containers or sidecars that fail before the main application starts, as their stderr is only accessible via `--previous`.
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 CKS 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 CKS question in full detail.
Cluster Setup and Hardening — This question tests Cluster Setup and Hardening — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: kubectl logs <pod> --previous — Option A is correct because `kubectl logs <pod> --previous` retrieves the logs from the previous instance of a crashed or restarting container. When a pod is in CrashLoopBackOff, the current container may have already restarted, so the standard error output from the failed run is only available in the previous container's logs. This command specifically fetches those logs, which typically contain the stderr output that caused the crash.
What should I do if I get this CKS 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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