LFCS Essential Commands Practice Question
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?
⚠ Common exam trap
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.
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
✓
du -sh /* | sort -rh
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.
Answer analysis
Option-by-option breakdown
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.
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