LFCS Essential Commands Practice Question
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?
⚠ Common exam trap
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.
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
✓
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.
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.
- ✗
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.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.