LFCS Essential Commands Practice Question
Exhibit
Filesystem Size Used Avail Use% Mounted on /dev/sda1 20G 20G 0 100% /var
Refer to the exhibit. The /var partition is 100% full. Which command can be used to find the largest files in /var/log to free up space?
⚠ Common exam trap
Candidates often choose `ls -lS` (option A) because it sorts by size, but they overlook that it does not recurse into subdirectories, making it ineffective for a directory tree like /var/log that typically contains multiple subdirectories.
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 -ah /var/log | sort -rh | head
It uses `du -ah` to list all files and directories in /var/log with human-readable sizes, pipes the output to `sort -rh` to sort them in reverse numerical order (largest first), and then uses `head` to display only the top entries. This combination efficiently identifies the largest files consuming space, allowing the administrator to target specific files for cleanup.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
ls -lS /var/log
Why it's wrong here
ls -lS lists files in the current directory sorted by size, but does not recurse into subdirectories and may not show the largest items overall.
- ✗
find /var/log -size +100M
Why it's wrong here
This finds files larger than 100M but does not sort them by size.
- ✓
du -ah /var/log | sort -rh | head
Why this is correct
du recursively calculates disk usage, sorts by size human-readable, and head shows the top entries.
- ✗
df -h /var/log
Why it's wrong here
df shows filesystem usage, not the size of individual files or directories.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This LFCS practice question is part of Courseiva's free Linux Foundation certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the LFCS exam.