- A
The 'df' command is caching old data; run 'sync' and then 'df' again.
Why wrong: Caching is possible but not typical cause.
- B
The mount point on the client (e.g., /mnt/nfs) is on a local filesystem that is full, preventing writes to the NFS mount.
When the mount point directory itself is on a full filesystem, writes to that mount point fail.
- C
The NFS server is overloaded and not responding in time.
Why wrong: Would cause timeout, not 'no space left on device'.
- D
The NFS export has a quota limit that is lower than the actual filesystem capacity.
Why wrong: Quota would produce a different error.
Question 359 of 513
LFCS Storage Management Practice Question
This LFCS practice question tests your understanding of storage management. 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 company's backup script fails with an error indicating 'no space left on device' on an NFS mount. The administrator checks 'df -h' on the NFS client and sees the mount is at 90% usage. However, the NFS server shows the exported filesystem is only 50% full. 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 choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The mount point on the client (e.g., /mnt/nfs) is on a local filesystem that is full, preventing writes to the NFS mount.
Option B is correct because the NFS mount point on the client (e.g., /mnt/nfs) is itself a directory within a local filesystem. When the local filesystem is full, the kernel cannot create or update the mount point's directory entry, causing writes to the NFS share to fail with 'no space left on device' even though the remote filesystem has free space. This is a classic client-side vs. server-side space confusion.
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 'df' command is caching old data; run 'sync' and then 'df' again.
Why it's wrong here
Caching is possible but not typical cause.
- ✓
The mount point on the client (e.g., /mnt/nfs) is on a local filesystem that is full, preventing writes to the NFS mount.
Why this is correct
When the mount point directory itself is on a full filesystem, writes to that mount point fail.
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 NFS server is overloaded and not responding in time.
Why it's wrong here
Would cause timeout, not 'no space left on device'.
- ✗
The NFS export has a quota limit that is lower than the actual filesystem capacity.
Why it's wrong here
Quota would produce a different error.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume 'no space left on device' always refers to the remote filesystem, overlooking that the local mount point directory resides on a potentially full local filesystem.
Detailed technical explanation
How to think about this question
Under the hood, when a process writes to an NFS mount, the VFS layer on the client first checks the local directory entry for the mount point. If the local filesystem containing that directory is full, the kernel returns ENOSPC before any NFS RPC call is made. This is because the mount point itself is a dentry in the local filesystem, and the kernel must be able to update its metadata (e.g., timestamps) even for remote writes. In real-world scenarios, this often happens when /var or /tmp is used as an NFS mount point and fills up due to logs or temporary files.
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 LFCS 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.
- →
Storage Management — study guide chapter
Learn the concepts, then practise the questions
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FAQ
Questions learners often ask
What does this LFCS question test?
Storage Management — This question tests Storage Management — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The mount point on the client (e.g., /mnt/nfs) is on a local filesystem that is full, preventing writes to the NFS mount. — Option B is correct because the NFS mount point on the client (e.g., /mnt/nfs) is itself a directory within a local filesystem. When the local filesystem is full, the kernel cannot create or update the mount point's directory entry, causing writes to the NFS share to fail with 'no space left on device' even though the remote filesystem has free space. This is a classic client-side vs. server-side space confusion.
What should I do if I get this LFCS 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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Last reviewed: Jul 4, 2026
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