This LFCS practice question tests your understanding of essential commands. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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.
An administrator runs 'df -h' and notices that /dev/sda1 is 95% full. The administrator needs to identify the largest files in the filesystem. Which command sequence is most efficient?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "which command"
Why it matters: Tests specific CLI syntax. Recall the exact command and its required context — near-synonyms and partial matches are common distractors.
find / -type f -size +100M
Why wrong: Finds files larger than 100MB but does not sort or group.
ls -lR / | sort -k5 -rn
Why wrong: Recursive listing, very slow and not size-sorted accurately.
find / -type f -exec du -sh {} \;
Why wrong: Executes du for each file, very slow.
du -sh /* | sort -rh
Shows sizes of top-level directories sorted by size, efficient for identifying large directories.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
du -sh /* | sort -rh
Option D is correct because it efficiently identifies the largest directories and files at the top level of the filesystem using `du -sh /*` to summarize disk usage per top-level item, then pipes to `sort -rh` to sort by human-readable sizes in descending order. This avoids scanning every single file recursively, making it the fastest approach for a full filesystem.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
find / -type f -size +100M
Why it's wrong here
Finds files larger than 100MB but does not sort or group.
ls -lR / | sort -k5 -rn
Why it's wrong here
Recursive listing, very slow and not size-sorted accurately.
find / -type f -exec du -sh {} \;
Why it's wrong here
Executes du for each file, very slow.
du -sh /* | sort -rh
Why this is correct
Shows sizes of top-level directories sorted by size, efficient for identifying large directories.
Clue confirmation
The clue word "which command" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Linux Foundation often tests the misconception that listing all files with `ls -lR` or scanning every file with `find` is efficient for disk usage analysis, when in reality summarizing with `du` on directories is far faster and more practical.
Detailed technical explanation
The `du -sh /*` command uses `du` (disk usage) with the `-s` flag to summarize each top-level directory or file, and `-h` for human-readable output. Piping to `sort -rh` sorts by size in descending order using GNU sort's human-numeric comparison. This approach is efficient because it reads the filesystem metadata once per top-level entry rather than traversing every inode, which is critical when dealing with a nearly full disk where performance matters.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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FAQ
Essential Commands — This question tests Essential Commands — Read the scenario before looking for a memorised answer..
The correct answer is: du -sh /* | sort -rh — Option D is correct because it efficiently identifies the largest directories and files at the top level of the filesystem using `du -sh /*` to summarize disk usage per top-level item, then pipes to `sort -rh` to sort by human-readable sizes in descending order. This avoids scanning every single file recursively, making it the fastest approach for a full filesystem.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Yes — watch for: "which command". Tests specific CLI syntax. Recall the exact command and its required context — near-synonyms and partial matches are common distractors.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 30, 2026
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