This LFCS practice question tests your understanding of essential commands. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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
/dev/sda1 on / type ext4 (rw,relatime,errors=remount-ro)
/dev/sda2 on /var type ext4 (rw,relatime)
tmpfs on /run type tmpfs (rw,nosuid,nodev)
/dev/sdb1 on /backup type ext4 (ro)
Refer to the exhibit.
A user attempts to create a file in /backup/snapshots/ but receives an error. What is the most likely cause?
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.
/dev/sda1 on / type ext4 (rw,relatime,errors=remount-ro)
/dev/sda2 on /var type ext4 (rw,relatime)
tmpfs on /run type tmpfs (rw,nosuid,nodev)
/dev/sdb1 on /backup type ext4 (ro)
A
The /backup filesystem is mounted read-only.
The '(ro)' flag indicates a read-only mount.
B
The /backup directory does not exist.
Why wrong: The mount point exists; the error is likely not about missing directory.
C
The user does not have write permission on /backup.
Why wrong: Even with write permissions, the read-only mount prevents writes.
D
The /backup filesystem is full.
Why wrong: Not indicated; a full filesystem would give a 'no space left' error, but the mount flag is the primary issue.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The /backup filesystem is mounted read-only.
The error occurs because the /backup filesystem is mounted read-only, which prevents any write operations, including file creation, regardless of directory permissions or available space. This is a common scenario when a filesystem is intentionally mounted with the 'ro' option in /etc/fstab or via the mount command to protect data integrity.
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 /backup filesystem is mounted read-only.
Why this is correct
The '(ro)' flag indicates a read-only mount.
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 /backup directory does not exist.
Why it's wrong here
The mount point exists; the error is likely not about missing directory.
✗
The user does not have write permission on /backup.
Why it's wrong here
Even with write permissions, the read-only mount prevents writes.
✗
The /backup filesystem is full.
Why it's wrong here
Not indicated; a full filesystem would give a 'no space left' error, but the mount flag is the primary issue.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often focus on file permissions or disk space, overlooking the filesystem-level mount option that overrides all other write mechanisms.
Detailed technical explanation
How to think about this question
When a filesystem is mounted read-only, the kernel enforces a read-only flag at the VFS (Virtual File System) layer, blocking all write system calls (e.g., write(), creat()) regardless of file permissions or ownership. This is typically configured via the 'ro' mount option in /etc/fstab or the mount command, and can be verified with 'mount | grep /backup' or 'cat /proc/mounts'. In real-world scenarios, this is often used for backup archives or ISO images to prevent accidental modification.
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 LFCS 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.
Essential Commands — This question tests Essential Commands — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The /backup filesystem is mounted read-only. — The error occurs because the /backup filesystem is mounted read-only, which prevents any write operations, including file creation, regardless of directory permissions or available space. This is a common scenario when a filesystem is intentionally mounted with the 'ro' option in /etc/fstab or via the mount command to protect data integrity.
What should I do if I get this LFCS 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.
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 →
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
This LFCS practice question is part of Courseiva's free Linux Foundation 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 LFCS exam.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.