LPIC-1 Devices, Filesystems and FHS Practice Question
This LPIC-1 practice question tests your understanding of devices, filesystems and fhs. 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.
After running 'df -h', the administrator sees that /dev/sda1 is 100% used. 'du -sh /mountpoint' shows only 50% used. 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
✓
A large file was deleted but a process still holds it open
When a file is deleted but a process still holds an open file descriptor to it, the kernel does not release the disk space until the process closes the file. The 'df' command reports space usage based on the filesystem's superblock, which still counts the deleted file's blocks. 'du' calculates space by traversing the directory tree and summing file sizes, so it does not see the unlinked file. This discrepancy explains why 'df' shows 100% usage while 'du' shows only 50%.
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 disk has bad blocks
Why it's wrong here
Incorrect: Bad blocks would not cause space usage discrepancy.
✓
A large file was deleted but a process still holds it open
Why this is correct
Correct: The file remains on disk until the process releases it.
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.
✗
There is a hard link that du does not count
Why it's wrong here
Incorrect: du counts actual data, hard links share the same inode.
✗
The filesystem is corrupted and needs fsck
Why it's wrong here
Incorrect: Corruption would not cause such a consistent discrepancy.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume 'du' and 'df' should always match, overlooking the fact that 'du' cannot account for space used by unlinked files still held open by processes.
Detailed technical explanation
How to think about this question
Under the hood, when a file is deleted (unlinked), its inode's link count drops to zero, but if a process has the file open, the inode remains allocated and its blocks are still accounted for in the filesystem's block bitmap. The 'lsof' command can list such processes with the 'deleted' flag in the file path. This scenario is common on busy servers with log files that are rotated while being written to by a daemon, causing gradual disk exhaustion until the process is restarted.
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 LPIC-1 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.
Devices, Filesystems and FHS — This question tests Devices, Filesystems and FHS — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: A large file was deleted but a process still holds it open — When a file is deleted but a process still holds an open file descriptor to it, the kernel does not release the disk space until the process closes the file. The 'df' command reports space usage based on the filesystem's superblock, which still counts the deleted file's blocks. 'du' calculates space by traversing the directory tree and summing file sizes, so it does not see the unlinked file. This discrepancy explains why 'df' shows 100% usage while 'du' shows only 50%.
What should I do if I get this LPIC-1 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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