The answer is that the disk space reaching 100% capacity is the most likely root cause of the application failure. When the filesystem is completely full, the operating system cannot perform any new write operations, which directly prevents the application from writing its logs or saving any other critical data. This is a fundamental limitation of any storage system: without free space, write-dependent processes halt immediately. On the CompTIA Cloud+ CV0-004 exam, this scenario tests your ability to correlate log analysis with disk space root cause in cloud environments like EC2, where log rotation is often misconfigured or monitoring alerts are missing. A common trap is to blame the application code or network latency, but the logs themselves will typically show write errors or "no space left on device" messages. Memory tip: think of a full disk like a full coffee cup—nothing more can be poured in until you empty it.
CV0-004 Operations and Support Practice Question
This CV0-004 practice question tests your understanding of operations and support. 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.
Exhibit
Refer to the exhibit.
```
CloudWatch Logs: /var/log/syslog
2024-03-15T10:00:00Z [ERROR] Disk space usage: 95%
2024-03-15T10:05:00Z [ERROR] Disk space usage: 97%
2024-03-15T10:10:00Z [WARN] Application X: unable to write log file
2024-03-15T10:11:00Z [CRITICAL] Application X: out of memory
2024-03-15T10:12:00Z [INFO] Instance i-12345: state changing to stopping
```
Refer to the exhibit. A cloud engineer is reviewing logs from an EC2 instance. Which of the following is the MOST likely root cause of the application failure?
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.
Refer to the exhibit.
```
CloudWatch Logs: /var/log/syslog
2024-03-15T10:00:00Z [ERROR] Disk space usage: 95%
2024-03-15T10:05:00Z [ERROR] Disk space usage: 97%
2024-03-15T10:10:00Z [WARN] Application X: unable to write log file
2024-03-15T10:11:00Z [CRITICAL] Application X: out of memory
2024-03-15T10:12:00Z [INFO] Instance i-12345: state changing to stopping
```
A
The application experienced a segmentation fault due to a code bug
Why wrong: No segmentation fault recorded; the failure is preceded by disk warnings.
B
The instance ran out of memory because the application had a memory leak
Why wrong: Out of memory is a consequence of disk full causing log failures.
C
The instance was stopped by the cloud provider due to a license violation
Why wrong: No indication of license issues; the stop follows critical errors.
D
The disk space reached 100% capacity, preventing the application from writing logs
The sequence shows disk warnings before application failures.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The disk space reached 100% capacity, preventing the application from writing logs
When disk space reaches 100% capacity, the operating system cannot write new data to the filesystem. Since the application relies on writing logs (and potentially other data) to disk, it will fail when it cannot perform these write operations. This is a common root cause in cloud environments where log rotation is not configured or monitoring thresholds are not set.
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 application experienced a segmentation fault due to a code bug
Why it's wrong here
No segmentation fault recorded; the failure is preceded by disk warnings.
✗
The instance ran out of memory because the application had a memory leak
Why it's wrong here
Out of memory is a consequence of disk full causing log failures.
✗
The instance was stopped by the cloud provider due to a license violation
Why it's wrong here
No indication of license issues; the stop follows critical errors.
✓
The disk space reached 100% capacity, preventing the application from writing logs
Why this is correct
The sequence shows disk warnings before application failures.
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
CompTIA often tests the distinction between memory-related failures (segfaults, OOM) and disk-related failures, where candidates mistakenly attribute a log-write failure to a memory issue instead of checking disk space.
Detailed technical explanation
How to think about this question
On Linux systems, when the filesystem is 100% full, write() system calls return ENOSPC (No space left on device). The application may not handle this error gracefully, leading to a crash or hang. The 'df -h' command would show 100% usage on the relevant mount point, and 'dmesg' might show filesystem errors. In AWS, CloudWatch metrics for 'DiskSpaceUtilization' can be used to alert before this occurs.
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 CV0-004 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.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Operations and Support — This question tests Operations and Support — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The disk space reached 100% capacity, preventing the application from writing logs — When disk space reaches 100% capacity, the operating system cannot write new data to the filesystem. Since the application relies on writing logs (and potentially other data) to disk, it will fail when it cannot perform these write operations. This is a common root cause in cloud environments where log rotation is not configured or monitoring thresholds are not set.
What should I do if I get this CV0-004 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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