- A
Use `mdadm --create --level=10 --raid-devices=4 --chunk=512 --metadata=1.2 /dev/md0 /dev/sda /dev/sdb /dev/sdc /dev/sdd` without --assume-clean and then run fsck.
Why wrong: This would likely overwrite data as mdadm initializes the array.
- B
Run `mdadm --examine --scan` to probe for superblocks on all disks, then attempt recovery with --super-minor or --uuid.
Why wrong: If superblock is missing, this won't help.
- C
Use `dd` to backup each disk's first few sectors, then use a data recovery tool.
Why wrong: This is a last resort, not the best first action.
- D
Use `mdadm --create --level=10 --raid-devices=4 --chunk=512 --metadata=1.2 --assume-clean /dev/md0 /dev/sda /dev/sdb /dev/sdc /dev/sdd` and then mount.
--assume-clean writes new superblocks but does not modify data areas, preserving data.
LPIC-2 Practice Question: Block Devices, Filesystems and Advanced Storage
This LPIC-2 practice question tests your understanding of block devices, filesystems and advanced storage. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 company runs a database server on Linux with a 4-disk RAID 10 array using mdadm. The server recently experienced a power outage. After reboot, the array is not assembling automatically. The administrator runs `mdadm --assemble --scan` and it fails with a message: 'mdadm: /dev/md0 has been found but is not a valid md superblock.' The administrator checks /proc/mdstat and sees no arrays. The disks /dev/sda, /dev/sdb, /dev/sdc, /dev/sdd are present. Running `mdadm --examine /dev/sda` shows no md superblock, but the disk contains data partitions. The administrator suspects that the superblock may be corrupted or that the disks were accidentally overwritten. The administrator has documentation that the array was created with the following parameters: RAID level 10, 4 disks, chunk size 512 KiB, metadata 1.2. What is the best course of action to recover the array?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"best"Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
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
Use `mdadm --create --level=10 --raid-devices=4 --chunk=512 --metadata=1.2 --assume-clean /dev/md0 /dev/sda /dev/sdb /dev/sdc /dev/sdd` and then mount.
Option D is correct because when the md superblock is missing or corrupted on all disks (as confirmed by `mdadm --examine` showing no superblock), the only way to recover the array is to recreate it with `--assume-clean`. This tells mdadm to trust that the data on the disks is already in a consistent RAID 10 layout without performing an initial resync, which would overwrite the existing data. The parameters must exactly match the original creation (RAID 10, 4 disks, chunk 512 KiB, metadata 1.2) to reconstruct the correct data mapping.
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.
- ✗
Use `mdadm --create --level=10 --raid-devices=4 --chunk=512 --metadata=1.2 /dev/md0 /dev/sda /dev/sdb /dev/sdc /dev/sdd` without --assume-clean and then run fsck.
Why it's wrong here
This would likely overwrite data as mdadm initializes the array.
- ✗
Run `mdadm --examine --scan` to probe for superblocks on all disks, then attempt recovery with --super-minor or --uuid.
Why it's wrong here
If superblock is missing, this won't help.
- ✗
Use `dd` to backup each disk's first few sectors, then use a data recovery tool.
Why it's wrong here
This is a last resort, not the best first action.
- ✓
Use `mdadm --create --level=10 --raid-devices=4 --chunk=512 --metadata=1.2 --assume-clean /dev/md0 /dev/sda /dev/sdb /dev/sdc /dev/sdd` and then mount.
Why this is correct
--assume-clean writes new superblocks but does not modify data areas, preserving data.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates mistakenly think `--create` always destroys data, but with `--assume-clean` it reconstructs the metadata without overwriting existing data, making it the correct recovery step when superblocks are lost.
Detailed technical explanation
How to think about this question
Metadata 1.2 stores the superblock at 4 KiB from the start of the device, leaving the first 4 KiB free for boot sectors. When a power outage corrupts the superblock, the data blocks remain intact because RAID 10 stripes and mirrors data across disks; recreating with `--assume-clean` avoids a destructive resync by assuming the data is already consistent. In real-world scenarios, this approach is the standard recovery method for mdadm arrays with lost superblocks, provided the exact original parameters are known.
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 LPIC-2 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
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 LPIC-2 question test?
Block Devices, Filesystems and Advanced Storage — This question tests Block Devices, Filesystems and Advanced Storage — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use `mdadm --create --level=10 --raid-devices=4 --chunk=512 --metadata=1.2 --assume-clean /dev/md0 /dev/sda /dev/sdb /dev/sdc /dev/sdd` and then mount. — Option D is correct because when the md superblock is missing or corrupted on all disks (as confirmed by `mdadm --examine` showing no superblock), the only way to recover the array is to recreate it with `--assume-clean`. This tells mdadm to trust that the data on the disks is already in a consistent RAID 10 layout without performing an initial resync, which would overwrite the existing data. The parameters must exactly match the original creation (RAID 10, 4 disks, chunk 512 KiB, metadata 1.2) to reconstruct the correct data mapping.
What should I do if I get this LPIC-2 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: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 25, 2026
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