The answer is the /var partition is full. This is the most likely cause because the application error stems from an inability to write logs to /var/log, and the df output shows the root filesystem—which contains /var in a typical single-partition layout—at 95% capacity, leaving insufficient space for new log entries. On the CompTIA Cloud+ CV0-004 exam, this scenario tests your ability to correlate application failures with filesystem full troubleshooting, a common real-world issue where a full partition prevents critical services from writing data. A frequent trap is confusing disk space exhaustion with inode exhaustion; while both can produce similar errors, df displays space usage, not inode counts, making space the more direct culprit here. Remember: when an app fails to write, always check df first for space, then df -i for inodes—space fills faster than inodes in most cloud environments.
CV0-004 Troubleshooting Practice Question
This CV0-004 practice question tests your understanding of troubleshooting. 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.
Exhibit
Refer to the exhibit.
Filesystem Size Used Avail Use% Mounted on
/dev/xvda1 20G 19G 1.0G 95% /
tmpfs 1.9G 0 1.9G 0% /dev/shm
Application error: 'No space left on device' when writing to /var/log/app.log.
The exhibit shows the output of the df command and an application error. What is the most likely cause of the error?
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.
Filesystem Size Used Avail Use% Mounted on
/dev/xvda1 20G 19G 1.0G 95% /
tmpfs 1.9G 0 1.9G 0% /dev/shm
Application error: 'No space left on device' when writing to /var/log/app.log.
A
The /dev/shm partition is full.
Why wrong: The /dev/shm partition is shown as 0% used.
B
The /var partition is full.
The root partition is at 95% usage, and since /var is under /, it is likely full.
C
The filesystem is corrupt.
Why wrong: Filesystem corruption would typically show different symptoms.
D
The inode usage on the root filesystem is exhausted.
Why wrong: While possible, df output shows space usage, and the more likely cause based on the data is space exhaustion.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The /var partition is full.
Option A is correct because the root partition is at 95% usage, and the application writes to /var/log which is on the root filesystem. Option B is wrong because tmpfs is empty. Option C is plausible but df shows space, not inodes; inode exhaustion would also give same error, but more likely space. Option D is wrong because no corruption indicated.
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 /dev/shm partition is full.
Why it's wrong here
The /dev/shm partition is shown as 0% used.
✓
The /var partition is full.
Why this is correct
The root partition is at 95% usage, and since /var is under /, it is likely full.
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 filesystem is corrupt.
Why it's wrong here
Filesystem corruption would typically show different symptoms.
✗
The inode usage on the root filesystem is exhausted.
Why it's wrong here
While possible, df output shows space usage, and the more likely cause based on the data is space exhaustion.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Trap categories for this question
Command / output trap
The /dev/shm partition is shown as 0% used.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→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 CV0-004 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Troubleshooting — This question tests Troubleshooting — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The /var partition is full. — Option A is correct because the root partition is at 95% usage, and the application writes to /var/log which is on the root filesystem. Option B is wrong because tmpfs is empty. Option C is plausible but df shows space, not inodes; inode exhaustion would also give same error, but more likely space. Option D is wrong because no corruption indicated.
What should I do if I get this CV0-004 question wrong?
Identify which CV0-004 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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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