- A
mdadm --create /dev/md0 --level=mirror --raid-disks=2 /dev/sdb /dev/sdc
Why wrong: --raid-disks is incorrect; should be --raid-devices. Also 'mirror' is an alias for 1 but may not be consistent.
- B
mdadm --create /dev/md0 --level=raid1 --add /dev/sdb /dev/sdc
Why wrong: --add is not used for creation; it's for adding a device to an existing array.
- C
mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/sdb /dev/sdc
Correct syntax for creating RAID1.
- D
mdadm --assemble /dev/md0 /dev/sdb /dev/sdc
Why wrong: --assemble is for assembling an existing array, not creating.
Question 278 of 513
LFCS Storage Management Practice Question
This LFCS practice question tests your understanding of storage management. 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.
A system administrator wants to create a RAID 1 array using two whole disks /dev/sdb and /dev/sdc. They plan to use mdadm. Which command creates the array and builds it with two devices?
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.
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
✓
mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/sdb /dev/sdc
Option C is correct because it uses the proper mdadm syntax to create a RAID 1 array: `--create` to initialize the array, `--level=1` (or `--level=raid1`) to specify mirroring, `--raid-devices=2` to indicate exactly two disks, and lists both `/dev/sdb` and `/dev/sdc`. This command builds the array with the two specified whole disks, which is the standard method for creating a RAID 1 array in Linux.
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.
- ✗
mdadm --create /dev/md0 --level=mirror --raid-disks=2 /dev/sdb /dev/sdc
Why it's wrong here
--raid-disks is incorrect; should be --raid-devices. Also 'mirror' is an alias for 1 but may not be consistent.
- ✗
mdadm --create /dev/md0 --level=raid1 --add /dev/sdb /dev/sdc
Why it's wrong here
--add is not used for creation; it's for adding a device to an existing array.
- ✓
mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/sdb /dev/sdc
Why this is correct
Correct syntax for creating RAID1.
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.
- ✗
mdadm --assemble /dev/md0 /dev/sdb /dev/sdc
Why it's wrong here
--assemble is for assembling an existing array, not creating.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse `--raid-devices` with `--raid-disks` or misuse `--add` for creation, leading them to pick options that either use invalid syntax or perform the wrong operation entirely.
Detailed technical explanation
How to think about this question
RAID 1 (mirroring) writes identical data to both disks, providing redundancy; mdadm uses a superblock to store array metadata on each device. When creating the array, mdadm writes a superblock to each disk, and the array must be assembled (via `--assemble` or automatically at boot) to be used. A common real-world scenario is using `--verbose` to monitor the resync process, which occurs after creation and can take time depending on disk size.
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 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.
Quick reference
RAID Level Comparison
| RAID Level | Min Disks | Fault Tolerance | Read | Write | Usable Capacity |
|---|---|---|---|---|---|
| RAID 0 | 2 | None | Excellent | Excellent | 100% |
| RAID 1 | 2 | 1 disk | Good | Moderate | 50% |
| RAID 5 | 3 | 1 disk | Good | Moderate | 67–94% |
| RAID 6 | 4 | 2 disks | Good | Lower | 50–88% |
| RAID 10 | 4 | 1 disk per mirror | Excellent | Good | 50% |
RAID is not a backup strategy — it protects against disk failure but not against accidental deletion, ransomware, or site-level events.
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.
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FAQ
Questions learners often ask
What does this LFCS question test?
Storage Management — This question tests Storage Management — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/sdb /dev/sdc — Option C is correct because it uses the proper mdadm syntax to create a RAID 1 array: `--create` to initialize the array, `--level=1` (or `--level=raid1`) to specify mirroring, `--raid-devices=2` to indicate exactly two disks, and lists both `/dev/sdb` and `/dev/sdc`. This command builds the array with the two specified whole disks, which is the standard method for creating a RAID 1 array in Linux.
What should I do if I get this LFCS 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: "which command". Tests specific CLI syntax. Recall the exact command and its required context — near-synonyms and partial matches are common distractors.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jul 4, 2026
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.
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