This CKAD practice question tests your understanding of application deployment. 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.
During a deployment update, the rollout is stuck and new pods are not becoming ready. The developer checks the events and sees 'Back-off restarting failed container'. 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's entrypoint command fails immediately after start
The 'Back-off restarting failed container' event indicates that the container process exits immediately after starting, causing Kubernetes to repeatedly restart it with increasing back-off delays. This is most commonly caused by a container entrypoint or command that fails at runtime, such as a misconfigured binary, missing dependency, or incorrect startup script. Unlike probe failures, which cause restarts after the container is already running, this error occurs before the container can even become ready.
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 liveness probe is failing
Why it's wrong here
Liveness failure restarts container but not necessarily back-off unless repeated.
✓
The container's entrypoint command fails immediately after start
Why this is correct
If the command exits, the container crashes, leading to restart back-off.
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.
✗
The image pull secret is missing
Why it's wrong here
Missing secret gives 'ErrImagePull' or 'ImagePullBackOff'.
✗
The pod exceeds its memory limit and is OOMKilled
Why it's wrong here
OOMKill shows 'OOMKilled' not back-off.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse 'Back-off restarting failed container' with liveness probe failures, but the key distinction is timing: this event occurs immediately at container start, while probe failures happen after the container has been running for some time.
Trap categories for this question
Command / output trap
OOMKill shows 'OOMKilled' not back-off.
Detailed technical explanation
How to think about this question
When a container exits with a non-zero exit code immediately after start, the kubelet records the exit code and increments the restart count, applying an exponential back-off (starting at 10s, doubling up to 5 minutes) as defined in the Kubernetes source code (pkg/kubelet/kuberuntime/kuberuntime_manager.go). This differs from probe failures, which trigger restarts via the kubelet's syncLoop but do not use the same back-off mechanism for the initial start failure. In real-world scenarios, this often occurs when a container's ENTRYPOINT script references a file or binary that is not present in the image, or when environment variables required at startup are missing.
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 CKAD 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 CKAD question in full detail.
Application Deployment — This question tests Application Deployment — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The container's entrypoint command fails immediately after start — The 'Back-off restarting failed container' event indicates that the container process exits immediately after starting, causing Kubernetes to repeatedly restart it with increasing back-off delays. This is most commonly caused by a container entrypoint or command that fails at runtime, such as a misconfigured binary, missing dependency, or incorrect startup script. Unlike probe failures, which cause restarts after the container is already running, this error occurs before the container can even become ready.
What should I do if I get this CKAD 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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