LPIC-1 Devices, Filesystems and FHS Practice Question
Network Topology
Refer to the exhibit. A user tries to write to /mnt/usb/myfile.txt as a non-root user and receives a permission denied error. What is the most likely reason?
⚠ Common exam trap
A common mix-up: candidates assume the 'permission denied' error must be due to file permissions (option D) or a read-only mount (option A), but they overlook that vfat does not store Unix permissions and that mount masks are the actual controlling mechanism.
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 vfat filesystem does not support Unix permissions, and the mount options (fmask/dmask) restrict write access to root only
The vfat filesystem does not store Unix-style permissions; instead, it relies on mount options like fmask and dmask to set the effective permissions for all files and directories. If these masks are set to restrict write access to root only (e.g., fmask=0133), non-root users will receive a 'permission denied' error even if the filesystem is mounted read-write. This is a common cause of write failures on USB drives formatted with FAT/VFAT.
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 filesystem is mounted read-only
Why it's wrong here
The mount output shows (rw) indicating read-write.
- ✓
The vfat filesystem does not support Unix permissions, and the mount options (fmask/dmask) restrict write access to root only
Why this is correct
Correct. The vfat filesystem does not store Unix permissions; the fmask and dmask options control the permissions shown. With fmask=0022, files get 755 permissions, but the owner is root (default unless uid/gid options are used). So only root can write.
- ✗
The filesystem is mounted with the 'noexec' option, preventing write
Why it's wrong here
The mount output does not show 'noexec'; it shows 'rw' and other options, but noexec is not present.
- ✗
The file's permissions are 644, so the user does not have write access
Why it's wrong here
The file shows -rw-r--r--, which allows owner write, but the owner is root, not the user.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This LPIC-1 practice question is part of Courseiva's free LPI 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 LPIC-1 exam.