- A
Reinstall GRUB to the Master Boot Record
Why wrong: Reinstalling GRUB addresses bootloader issues, not kernel panic due to missing root filesystem.
- B
Boot from a rescue disk and rebuild the initramfs with the necessary filesystem modules
Rebuilding initramfs includes required modules for root filesystem access.
- C
Run fsck on the root partition to check for filesystem corruption
Why wrong: fsck repairs filesystem errors but does not fix missing drivers or wrong root= parameter.
- D
Check the kernel command line in the bootloader configuration for the correct root= parameter
Incorrect root= parameter prevents the kernel from finding the root filesystem.
- E
Disable SELinux by adding selinux=0 to the kernel command line
Why wrong: SELinux does not affect the kernel's ability to mount the root filesystem.
Quick Answer
The correct actions are to rebuild the initramfs from a rescue disk and to check the kernel command line in the bootloader configuration for the correct root= parameter. This "VFS: Unable to mount root fs" error occurs because the kernel cannot locate or mount the root filesystem, often due to missing filesystem drivers in the initramfs or an incorrect root device identifier. On the CompTIA Linux+ XK0-005 exam, this scenario tests your understanding of the boot process, specifically how the kernel relies on the initramfs for driver loading and the root= parameter for partition identification. A common trap is assuming the filesystem itself is corrupt, when the real issue is a typo in the UUID or device name in GRUB. Remember the mnemonic "Root and Ram" — always verify the root= parameter and rebuild the initramfs to ensure the necessary drivers are present.
XK0-005 Troubleshooting Practice Question
This XK0-005 practice question tests your understanding of troubleshooting. 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 Linux engineer is troubleshooting a server that fails to boot. The server displays a message indicating 'Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)'. Which TWO actions should the engineer take to resolve this issue? (Choose TWO.)
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
Boot from a rescue disk and rebuild the initramfs with the necessary filesystem modules
The error 'Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)' indicates the kernel cannot locate or mount the root filesystem. Option B is correct because rebuilding the initramfs from a rescue disk ensures the necessary filesystem drivers (e.g., ext4, xfs) are included, which may have been missing or corrupted. Option D is correct because the root= parameter in the bootloader configuration (e.g., GRUB) tells the kernel which device/partition to mount as root; a typo or incorrect value (e.g., wrong UUID or device name) will cause this exact panic.
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.
- ✗
Reinstall GRUB to the Master Boot Record
Why it's wrong here
Reinstalling GRUB addresses bootloader issues, not kernel panic due to missing root filesystem.
- ✓
Boot from a rescue disk and rebuild the initramfs with the necessary filesystem modules
Why this is correct
Rebuilding initramfs includes required modules for root filesystem access.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Run fsck on the root partition to check for filesystem corruption
Why it's wrong here
fsck repairs filesystem errors but does not fix missing drivers or wrong root= parameter.
- ✓
Check the kernel command line in the bootloader configuration for the correct root= parameter
Why this is correct
Incorrect root= parameter prevents the kernel from finding the root filesystem.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Disable SELinux by adding selinux=0 to the kernel command line
Why it's wrong here
SELinux does not affect the kernel's ability to mount the root filesystem.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse a kernel panic about root filesystem mounting with a bootloader or filesystem corruption issue, leading them to choose GRUB reinstallation (A) or fsck (C) instead of addressing the initramfs or kernel command line.
Detailed technical explanation
How to think about this question
The initramfs (initial RAM filesystem) contains kernel modules needed to access the root filesystem, such as storage controller drivers (e.g., ahci, nvme) and filesystem drivers (e.g., ext4, btrfs). If the initramfs lacks these modules or is corrupted, the kernel cannot mount the root device, triggering the panic. The root= parameter can specify a device node (e.g., /dev/sda1), a UUID (e.g., root=UUID=...), or a LABEL; using a UUID is preferred because device names can change between boots.
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 XK0-005 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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Troubleshooting — study guide chapter
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FAQ
Questions learners often ask
What does this XK0-005 question test?
Troubleshooting — This question tests Troubleshooting — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Boot from a rescue disk and rebuild the initramfs with the necessary filesystem modules — The error 'Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)' indicates the kernel cannot locate or mount the root filesystem. Option B is correct because rebuilding the initramfs from a rescue disk ensures the necessary filesystem drivers (e.g., ext4, xfs) are included, which may have been missing or corrupted. Option D is correct because the root= parameter in the bootloader configuration (e.g., GRUB) tells the kernel which device/partition to mount as root; a typo or incorrect value (e.g., wrong UUID or device name) will cause this exact panic.
What should I do if I get this XK0-005 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Same concept, more angles
1 more ways this is tested on XK0-005
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A user reports that a Linux workstation fails to boot and displays 'Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)'. Which of the following is the most likely cause?
easy- A.A filesystem listed in /etc/fstab has errors.
- B.A memory module is faulty.
- C.The boot loader is missing or corrupted.
- ✓ D.The root filesystem device is incorrectly specified in the kernel command line.
Why D: The error 'VFS: Unable to mount root fs on unknown-block(0,0)' indicates that the kernel cannot locate the root filesystem device. The most likely cause is that the root filesystem device is incorrectly specified in the kernel command line (e.g., via a bootloader parameter like root=), preventing the kernel from finding the correct block device to mount as root.
Last reviewed: Jun 11, 2026
This XK0-005 practice question is part of Courseiva's free CompTIA 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 XK0-005 exam.
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