This CKS practice question tests your understanding of cluster setup and hardening. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 is in a CrashLoopBackOff state. You run 'kubectl logs pod-name' and see: 'Error: failed to start container: exec: "/app": stat /app: no such file or directory'. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The container image is missing the /app executable
The error message 'exec: "/app": stat /app: no such file or directory' indicates that the container runtime (e.g., containerd) cannot find the executable specified in the container's ENTRYPOINT or CMD. This occurs when the container image does not include the /app binary or script at that path, causing the container to fail immediately on start and enter CrashLoopBackOff. Option D correctly identifies that the container image is missing the /app executable.
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.
✗
The pod is out of memory
Why it's wrong here
OOMKilled would show a different error message.
✗
The container's working directory is incorrect
Why it's wrong here
Working directory issues would not produce this exact error.
✗
The pod has a liveness probe that is failing
Why it's wrong here
A failing liveness probe would result in a restart, but the logs would not show this error.
✓
The container image is missing the /app executable
Why this is correct
Correct. The container is trying to run /app, but the file does not exist in the image.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
CNCF often tests the distinction between container startup failures (e.g., missing executable) and runtime failures (e.g., probe failures or resource limits), so candidates may confuse a liveness probe failure (which occurs after the container is running) with an exec error that prevents the container from starting at all.
Trap categories for this question
Command / output trap
OOMKilled would show a different error message.
Detailed technical explanation
How to think about this question
When a container is started, the container runtime (e.g., containerd or CRI-O) uses the image's metadata to set the entrypoint and command. The exec system call is made to the specified binary; if the binary is not present in the container's filesystem (i.e., not included in the image layers), the kernel returns ENOENT, which the runtime reports as 'no such file or directory'. This is distinct from a permissions error (EACCES) or a missing shared library (e.g., ELF interpreter). In real-world scenarios, this often happens when a Dockerfile's COPY or ADD instruction fails to place the binary at the expected path, or when the image is built for a different architecture.
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 small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
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: The container image is missing the /app executable — The error message 'exec: "/app": stat /app: no such file or directory' indicates that the container runtime (e.g., containerd) cannot find the executable specified in the container's ENTRYPOINT or CMD. This occurs when the container image does not include the /app binary or script at that path, causing the container to fail immediately on start and enter CrashLoopBackOff. Option D correctly identifies that the container image is missing the /app executable.
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: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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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