LPIC-1 System Architecture Practice Question
A Linux server has two hot-swappable SATA drives that are part of a software RAID 1 array. The administrator needs to replace one drive while the system is running, but first wants to verify the current status of the array to ensure it is not degraded. Which command will display the detailed status of the mdadm array?
⚠ Common exam trap
The trap here is assuming that /proc/mdstat provides all necessary details, but it only gives a summary and lacks the detailed component status needed for safe hot-swapping.
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
To verify the status of a software RAID array before replacing a drive, the administrator needs detailed information about the array's health and component devices. The mdadm --detail command provides this comprehensive view, including RAID level, state, and per-device status. This ensures the array is not already degraded and that the correct drive can be identified for replacement. Other commands either show only summary information or focus on physical drives rather than the RAID logical device.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
cat /proc/mdstat
Why it's wrong here
The /proc/mdstat file provides a brief summary of all md devices and their status, but it does not show detailed information such as the UUID, RAID level, chunk size, or the exact state of each component device. For a comprehensive status report, mdadm --detail is required. This command is useful for a quick check but insufficient for verifying detailed array health before hot-swapping a drive.
- ✓
mdadm --detail /dev/md0
Why this is correct
The mdadm --detail command displays comprehensive information about the specified array, including RAID level, array size, state (active/clean, degraded, etc.), UUID, and the status of each component device. This is exactly what the administrator needs to verify the array is not degraded and to confirm which drive can be safely replaced. It is the standard tool for detailed RAID inspection on Linux.
- ✗
smartctl -a /dev/sda
Why it's wrong here
smartctl -a retrieves S.M.A.R.T. health information for a specific physical drive, which can indicate impending hardware failure. However, it does not show the status of the RAID array itself, such as whether it is degraded or which member is out of sync. The administrator needs array-level status, not just individual drive health. This command is complementary but not the primary tool for verifying RAID status.
- ✗
fdisk -l /dev/sda
Why it's wrong here
fdisk -l lists partition tables of the specified disk, showing partitions and their sizes, but it does not report on RAID array status or component health. It cannot indicate whether a RAID 1 array is degraded or which drive is faulty. This command is used for partitioning tasks, not for monitoring software RAID. It would not help in verifying array status before a hot-swap.
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 and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official LPI exam blueprint
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.