The answer is that an incorrect UUID in /etc/fstab will cause the system to boot into an emergency shell. This happens because systemd reads the /etc/fstab file during the boot process to locate and mount filesystems, using the UUID as a unique identifier for block devices. When the UUID specified for the root filesystem does not match any available partition—often after a disk replacement—the mount operation fails, and since the root partition is critical for system operation, the boot process cannot continue normally, forcing the system into an emergency shell for manual repair. On the CompTIA Linux+ XK0-005 exam, this scenario tests your understanding of the boot sequence and filesystem mounting, and a common trap is confusing emergency shell with rescue mode or a kernel panic. Remember the tip: “UUID mismatch equals emergency shell, not a crash.”
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.
Exhibit
Refer to the exhibit.
# /etc/fstab
UUID=1234-5678-90ab-cdef / ext4 defaults 1 1
UUID=abcd-ef12-3456-7890 /boot ext4 defaults 1 2
UUID=90ab-cdef-1234-5678 /home ext4 defaults 1 2
# Note: The root filesystem UUID is incorrect because the disk was replaced.
A Linux system fails to boot after a disk replacement. The administrator examines /etc/fstab and sees the above. What is the most likely result of this configuration?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Refer to the exhibit.
# /etc/fstab
UUID=1234-5678-90ab-cdef / ext4 defaults 1 1
UUID=abcd-ef12-3456-7890 /boot ext4 defaults 1 2
UUID=90ab-cdef-1234-5678 /home ext4 defaults 1 2
# Note: The root filesystem UUID is incorrect because the disk was replaced.
A
The system will boot into an emergency shell
Root mount failure causes emergency mode.
B
The system will boot normally using the device name
Why wrong: Mount uses UUID, not device name, when UUID is specified.
C
The system will ignore the incorrect UUID and try next entry
Why wrong: Each entry is independent; root failure stops boot.
D
The system will prompt for manual fsck
Why wrong: fsck may not run if mount fails; systemd drops to emergency.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The system will boot into an emergency shell
The /etc/fstab entry contains an incorrect UUID for the root filesystem. During boot, systemd reads fstab and attempts to mount the root partition using the specified UUID. When the UUID does not match any available block device, the mount fails, and because the root filesystem is critical, the system drops into an emergency shell to allow manual intervention.
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.
✓
The system will boot into an emergency shell
Why this is correct
Root mount failure causes emergency mode.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The system will boot normally using the device name
Why it's wrong here
Mount uses UUID, not device name, when UUID is specified.
✗
The system will ignore the incorrect UUID and try next entry
Why it's wrong here
Each entry is independent; root failure stops boot.
✗
The system will prompt for manual fsck
Why it's wrong here
fsck may not run if mount fails; systemd drops to emergency.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume the system will fall back to the device name or skip the entry, but Linux strictly requires the exact UUID for mounting and will drop to an emergency shell on failure.
Detailed technical explanation
How to think about this question
Under the hood, systemd-fstab-generator converts fstab entries into mount units. If the root filesystem fails to mount, systemd enters emergency.target, which presents a minimal shell for recovery. In real-world scenarios, administrators often use 'blkid' to verify UUIDs after disk replacement, and can boot from a live ISO to correct fstab or use 'systemctl rescue' to access a recovery shell.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this XK0-005 question in full detail.
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: The system will boot into an emergency shell — The /etc/fstab entry contains an incorrect UUID for the root filesystem. During boot, systemd reads fstab and attempts to mount the root partition using the specified UUID. When the UUID does not match any available block device, the mount fails, and because the root filesystem is critical, the system drops into an emergency shell to allow manual intervention.
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.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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