LPIC-1 Devices, Filesystems and FHS Practice Question
A Linux system has a software RAID1 array /dev/md0 consisting of /dev/sda1 and /dev/sdb1. After replacing a failed disk, the administrator runs 'mdadm --manage /dev/md0 --add /dev/sdc1', but the array remains degraded. Which command should be used to check the status of the array?
⚠ Common exam trap
A common mix-up: candidates confuse `--examine` (which inspects a disk's superblock) with `--detail` (which shows the array's overall state), leading them to choose Option A when they need to check the array's degraded status rather than a single disk's metadata.
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 --detail /dev/md0
The `mdadm --detail /dev/md0` command displays the current state of the RAID array, including its status (e.g., degraded, active), the number of active and failed devices, and the sync/resync progress. Since the array remains degraded after adding a new disk, this command will show whether the new disk has been properly integrated or if there is an underlying issue, such as a missing or failed component.
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 --examine /dev/sdc1
Why it's wrong here
mdadm --examine reads the RAID superblock stored on a member device, so examining /dev/sdc1 shows only that disk's metadata, not the assembled array's state. It is tempting because it inspects RAID members, but it suits identifying a spare's superblock, not checking /dev/md0's degradation.
- ✗
mdadm --version
Why it's wrong here
mdadm --version prints the installed mdadm release number and exits; it reports nothing about any array's assembly, member disks or degraded status. It is tempting as a quick sanity check of tooling, but it is used when verifying software versions, not diagnosing a specific array.
- ✓
mdadm --detail /dev/md0
Why this is correct
`mdadm --detail /dev/md0` reports the array's current state, including which member devices are active, failed or spare, and the overall RAID1 redundancy level. This directly satisfies the stem's requirement to check why the array remains degraded after adding /dev/sdc1, showing whether the new device was actually incorporated.
- ✗
mdadm --query /dev/md0
Why it's wrong here
mdadm --query on /dev/md0 reports whether the device is an md array and its level, but omits member disk states, so it cannot reveal why the array stays degraded. It is tempting because it targets the array directly, but it suits identifying an unknown device, not detailed status.
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.
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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.