The correct step is to run blkid /dev/sda3 to find the new UUID and then update /etc/fstab. This is necessary because when a disk is replaced, the new device is assigned a different UUID, while the /etc/fstab file still references the old UUID from the original disk. The mount -a command fails because it cannot locate a device matching the stale identifier, so retrieving the current UUID with blkid and editing fstab restores the automatic mount. On the CompTIA Linux+ XK0-005 exam, this scenario tests your understanding of persistent block device naming and the critical role UUIDs play in avoiding boot or mount failures after hardware changes. A common trap is to assume the device name (like /dev/sda3) remains constant, but UUIDs are unique per filesystem and change with each new disk. Remember the mnemonic: "New disk, new UUID — blkid shows you what to do."
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.
# cat /etc/fstab
UUID=abc123 / ext4 defaults 0 1
UUID=def456 /boot ext4 defaults 0 2
UUID=ghi789 /home ext4 defaults 0 2
UUID=jkl012 swap swap defaults 0 0
# mount -a
mount: /home: special device UUID=ghi789 does not exist.
An administrator runs 'mount -a' and receives the error shown in the exhibit. The /home partition was recently removed and replaced with a new disk. Which of the following steps should the administrator take to resolve the issue?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Run 'blkid /dev/sda3' to find the new UUID and update /etc/fstab.
The error occurs because the /home partition was replaced with a new disk, so its UUID (or device identifier) in /etc/fstab no longer matches the actual disk. Running 'blkid /dev/sda3' retrieves the new UUID, which must then be updated in /etc/fstab so that 'mount -a' can mount the correct device automatically.
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.
✗
Run 'mount /dev/sda3 /home' to mount the partition manually.
Why it's wrong here
This works temporarily but does not fix the fstab entry for persistent mounting.
✗
Run 'fsck /dev/sda3' to check the filesystem.
Why it's wrong here
fsck checks filesystem integrity, not UUID mismatches.
✗
Run 'mkfs.ext4 /dev/sda3' to create a new filesystem.
Why it's wrong here
This would format the disk, which is destructive and unnecessary.
✓
Run 'blkid /dev/sda3' to find the new UUID and update /etc/fstab.
Why this is correct
blkid shows the new UUID, which can be used to replace the old UUID in fstab.
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 assume the filesystem is damaged or needs reformatting (options B or C), when in fact the error stems from a stale UUID reference in /etc/fstab after disk replacement.
Detailed technical explanation
How to think about this question
The 'mount -a' command reads /etc/fstab and attempts to mount all entries not already mounted. Each fstab entry can specify a device by UUID, label, or path; when a disk is replaced, the UUID changes, causing mount to fail with 'special device does not exist' or similar. Using 'blkid' to get the new UUID and updating fstab ensures persistent, correct mounting across reboots.
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: Run 'blkid /dev/sda3' to find the new UUID and update /etc/fstab. — The error occurs because the /home partition was replaced with a new disk, so its UUID (or device identifier) in /etc/fstab no longer matches the actual disk. Running 'blkid /dev/sda3' retrieves the new UUID, which must then be updated in /etc/fstab so that 'mount -a' can mount the correct device automatically.
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.
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Question Discussion
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