LFCS User and Group Management Practice Question
A user reports that they cannot execute a file even though they are in the file's group. The file has permissions 644 and group ownership 'staff'. The user is a member of 'staff'. What is the likely issue?
⚠ Common exam trap
LFCS exams often test the distinction between file ownership and group membership, trapping candidates who think being in the group automatically grants execute permission without checking the actual permission bits.
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 file lacks execute permission for the group
The file has permissions 644, which means the owner has read/write (6), the group has read-only (4), and others have read-only (4). Since the user is a member of the group 'staff' but not the owner, they fall under the group permission class. The group lacks execute permission (the 'x' bit), so the user cannot execute the file. Execute permission is required to run a file as a command or script, regardless of group membership.
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 file lacks execute permission for the group
Why this is correct
Permissions 644 grant read and write to the owner, and read only to group and others; no execute bit is set for any class. Group membership is irrelevant because the group triad is r--. Adding execute for the group, giving 654 or 754, is required before a 'staff' member can run the file.
- ✗
The file does not have the setgid bit
Why it's wrong here
The setgid bit governs group inheritance on new files in a directory, not execute permission. The 644 mode grants read and write to owner and group but no execute bit for anyone, which is the actual blocker. Setgid would matter for shared directories needing consistent group ownership.
- ✗
The user's primary group is not 'staff'
Why it's wrong here
Supplementary group membership suffices for group permission checks; the primary group need not be 'staff'. The real fault is mode 644, which carries no execute bit for the group class. Primary group configuration would matter when a process creates files needing a specific default group.
- ✗
The user is not the owner of the file
Why it's wrong here
Ownership is irrelevant here: the user already matches the group, and group permissions apply regardless of owner. Mode 644 simply omits the execute bit for owner, group and others, so no class can execute it. Ownership would matter if diagnosing owner-only access on a 744 file.
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JA
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.