LPIC-1 Devices, Filesystems and FHS Practice Question
An administrator needs to create a new ext4 filesystem on /dev/sdb1 and wants to reserve 2% of the blocks for the root user. Which command should be used?
⚠ Common exam trap
It's easy for candidates to confuse `-m` (reserved block percentage) with `-r` (revision level) or assume `tune2fs` can be used to create a filesystem, when in fact `tune2fs` only modifies existing filesystems.
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
✓
mkfs.ext4 -m 2 /dev/sdb1
The `-m` flag in `mkfs.ext4` specifies the percentage of filesystem blocks reserved for the root user (superuser). By default, ext4 reserves 5% of blocks; using `-m 2` reduces this to 2%, as required. This command creates a new ext4 filesystem on `/dev/sdb1` with the specified reserved block percentage.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
mkfs.ext4 -m 2 /dev/sdb1
Why this is correct
The `-m` flag on `mkfs.ext4` sets the percentage of filesystem blocks reserved for root, so `-m 2` reserves exactly 2%, satisfying the stem's constraint. It creates the ext4 filesystem on /dev/sdb1 in one step, unlike `tune2fs -m`, which only adjusts reservation on an existing filesystem.
- ✗
tune2fs -m 2 /dev/sdb1
Why it's wrong here
tune2fs alters an existing filesystem's parameters, so it cannot create the ext4 filesystem the task requires; running it on /dev/sdb1 before mkfs fails. It is tempting because -m 2 sets exactly the 2% reserved-blocks percentage, and it would be correct for adjusting that reserve on a filesystem that already exists.
- ✗
mke2fs -r 2 /dev/sdb1
Why it's wrong here
mke2fs has no -r option for reserved blocks; -r sets the filesystem revision, so the command errors or misconfigures rather than reserving 2%. It is tempting because mke2fs does create ext4 filesystems and -m 2 is the actual reserved-blocks flag, making this the right tool with the wrong flag.
- ✗
mkfs.ext4 -R 2 /dev/sdb1
Why it's wrong here
mkfs.ext4's -R option specifies extended filesystem features, not a reserved-blocks percentage, so 2 is rejected or misinterpreted. It is tempting because mkfs.ext4 genuinely creates the ext4 filesystem requested, and -m 2 would correctly reserve 2%; only the flag letter is wrong.
Go deeper
Related to this question
About these practice questions
This LPIC-1 question is part of Courseiva's 402-question bank — original exam-style content with full explanations and wrong-answer analysis, never real exam questions or exam dumps. Learn why practice questions differ from exam dumps →
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This LPIC-1 practice question is part of Courseiva's free LPI 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 LPIC-1 exam.