LPIC-1 System Architecture Practice Question
A system administrator is troubleshooting a Linux server that fails to boot. The server has a software RAID 1 configuration using mdadm, with the root filesystem located on /dev/md0. During boot, the system halts with the following error: 'VFS: Unable to mount root fs on unknown-block(0,0)'. The admin verifies that the BIOS recognizes all disks and that the RAID array was properly assembled prior to the last shutdown. The system was working after a recent kernel update, but now fails. Which of the following actions is the most likely solution?
⚠ Common exam trap
A common mix-up: candidates confuse a root filesystem mount failure with filesystem corruption (fsck) or bootloader issues, but the specific 'unknown-block(0,0)' error points to a missing kernel module or initramfs problem after a kernel update.
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
✓
Rebuild the initramfs to include the mdadm module and the RAID metadata.
After a kernel update, the new kernel may lack the necessary mdadm module or RAID metadata support in the initramfs. The error 'unknown-block(0,0)' indicates the kernel cannot find the root device because the initramfs does not contain the required RAID drivers or assembly instructions. Rebuilding the initramfs with the correct mdadm configuration ensures the kernel can assemble and mount /dev/md0 during boot.
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 a live CD to run fsck on /dev/md0.
Why it's wrong here
The device /dev/md0 may not be available in the initramfs; fsck cannot be run on an unmountable device.
- ✓
Rebuild the initramfs to include the mdadm module and the RAID metadata.
Why this is correct
Rebuilding the initramfs adds the necessary RAID support, allowing the kernel to assemble and mount /dev/md0.
- ✗
Check the /etc/fstab file for incorrect root device.
Why it's wrong here
/etc/fstab is only read after the root filesystem is mounted; the error occurs before that.
- ✗
Reinstall the bootloader on the MBR.
Why it's wrong here
The bootloader is functioning as it loads the kernel; reinstalling it does not address the missing root device.
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.