This KCNA practice question tests your understanding of kubernetes fundamentals. 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 in a ReplicaSet is failing with 'CrashLoopBackOff'. 'kubectl logs pod' shows 'Error: listen tcp :8080: bind: address already in use'. 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 process is not terminating quickly enough on SIGTERM, causing a port conflict on restart.
The error 'address already in use' on port 8080 indicates that when the container restarts, the previous process is still holding the port. This typically happens when the application does not handle SIGTERM properly and does not shut down within the terminationGracePeriodSeconds (default 30s), so the old process lingers while the new one tries to bind to the same port, causing a CrashLoopBackOff.
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 readiness probe is misconfigured.
Why it's wrong here
Readiness probe doesn't affect port binding.
✗
The container image is missing the application binary.
Why it's wrong here
Missing binary would give 'command not found'.
✓
The container's process is not terminating quickly enough on SIGTERM, causing a port conflict on restart.
Why this is correct
Old process still holds the port.
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 pod is using hostPort and two pods on the same node conflict.
Why it's wrong here
hostPort would cause conflict across pods, but single pod restart shows the same pod.
Common exam traps
Common exam trap: answer the scenario, not the keyword
CNCF often tests the distinction between pod startup failures caused by resource constraints or probe misconfiguration versus application-level port conflicts that arise from improper signal handling during restarts.
Trap categories for this question
Command / output trap
Missing binary would give 'command not found'.
Detailed technical explanation
How to think about this question
Under the hood, when a pod is terminated, Kubernetes sends a SIGTERM to the main process (PID 1) and waits for terminationGracePeriodSeconds (default 30s). If the application ignores SIGTERM or takes too long to release the socket, the kernel keeps the port in a TIME_WAIT or CLOSE_WAIT state. On restart, the new process cannot bind to the same port until the old socket is fully released. This is a common issue with applications that do not implement graceful shutdown or use frameworks that block signals.
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 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: The container's process is not terminating quickly enough on SIGTERM, causing a port conflict on restart. — The error 'address already in use' on port 8080 indicates that when the container restarts, the previous process is still holding the port. This typically happens when the application does not handle SIGTERM properly and does not shut down within the terminationGracePeriodSeconds (default 30s), so the old process lingers while the new one tries to bind to the same port, causing a CrashLoopBackOff.
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: "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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