- A
Remove the line from /etc/fstab and run systemctl daemon-reload, then reboot.
Why wrong: Removing the line works, but daemon-reload does not reload fstab; reboot is needed, but the option includes daemon-reload which is unnecessary and incorrect.
- B
Add the nofail option to the fstab line, then reboot.
Why wrong: nofail allows boot to continue, but the mount attempt will still fail silently; the requirement is to prevent the mount entirely, not just ignore failure.
- C
Delete the /data directory and reboot.
Why wrong: Deleting the mount point does not prevent the system from trying to mount the missing device; the failure will still occur.
- D
Use a text editor to insert '#' at the beginning of the /dev/sdb1 line in /etc/fstab, then reboot.
Commenting the line prevents the mount attempt; system will boot normally.
EX200 Deploy, configure, and maintain systems Practice Question
This EX200 practice question tests your understanding of deploy, configure, and maintain systems. 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 system administrator is troubleshooting a RHEL 9 server that fails to boot and drops into emergency mode. The system console shows an error about mounting /dev/sdb1 on /data. The administrator enters emergency mode, checks /etc/fstab, and sees the line: /dev/sdb1 /data ext4 defaults 0 0. The /data directory exists but /dev/sdb1 is a partition on an external USB drive that was removed. The administrator needs the system to boot normally without the USB drive and plans to fix the mount configuration later. Which course of action should the administrator take?
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
Use a text editor to insert '#' at the beginning of the /dev/sdb1 line in /etc/fstab, then reboot.
Option D is correct because commenting out the /dev/sdb1 line in /etc/fstab with '#' prevents systemd from attempting to mount the missing device during boot, allowing the system to boot normally into multi-user.target. This is a safe, reversible change that does not delete the mount point or alter the filesystem, and it preserves the original configuration for later restoration.
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.
- ✗
Remove the line from /etc/fstab and run systemctl daemon-reload, then reboot.
Why it's wrong here
Removing the line works, but daemon-reload does not reload fstab; reboot is needed, but the option includes daemon-reload which is unnecessary and incorrect.
- ✗
Add the nofail option to the fstab line, then reboot.
Why it's wrong here
nofail allows boot to continue, but the mount attempt will still fail silently; the requirement is to prevent the mount entirely, not just ignore failure.
- ✗
Delete the /data directory and reboot.
Why it's wrong here
Deleting the mount point does not prevent the system from trying to mount the missing device; the failure will still occur.
- ✓
Use a text editor to insert '#' at the beginning of the /dev/sdb1 line in /etc/fstab, then reboot.
Why this is correct
Commenting the line prevents the mount attempt; system will boot normally.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may think removing the line or adding nofail is the correct fix, but they overlook that the system is already in emergency mode and the immediate goal is to boot normally with minimal changes, making a simple comment-out the safest and most reversible action.
Detailed technical explanation
How to think about this question
When systemd encounters a mount entry in /etc/fstab, it generates a corresponding .mount unit. If the device is missing, the mount unit fails, and systemd enters emergency mode because the mount is marked with a non-zero pass number (the fifth field) or because the default failure action for critical mounts is to drop to emergency.target. Commenting out the line prevents systemd from generating the mount unit entirely, allowing the boot process to continue. In a real-world scenario, a sysadmin might also use 'systemctl mask' on the generated mount unit to achieve a similar effect without editing fstab, but the simplest and most direct method in emergency mode is to edit fstab with a text editor.
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 EX200 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.
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FAQ
Questions learners often ask
What does this EX200 question test?
Deploy, configure, and maintain systems — This question tests Deploy, configure, and maintain systems — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use a text editor to insert '#' at the beginning of the /dev/sdb1 line in /etc/fstab, then reboot. — Option D is correct because commenting out the /dev/sdb1 line in /etc/fstab with '#' prevents systemd from attempting to mount the missing device during boot, allowing the system to boot normally into multi-user.target. This is a safe, reversible change that does not delete the mount point or alter the filesystem, and it preserves the original configuration for later restoration.
What should I do if I get this EX200 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.
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Last reviewed: Jun 24, 2026
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