LFCS User and Group Management Practice Question
You are managing a Linux server that hosts a shared project directory /projects/alpha, owned by the group 'alpha' (GID 2001). The directory has permissions 2770 (setgid, rwx for owner and group, no access for others). User 'jane' (UID 1501) has a primary group 'staff' (GID 1001) and is not in the 'alpha' group. She reports being unable to list or modify files in /projects/alpha. You need to give her access as a member of the 'alpha' group without changing her primary group. Which command sequence should you use?
⚠ Common exam trap
LFCS often tests the difference between `-g` (change primary group) and `-aG` (append supplementary group) — candidates who omit `-a` accidentally wipe existing supplementary memberships.
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
✓
usermod -aG alpha jane
The command `usermod -aG alpha jane` appends jane to the supplementary group 'alpha' without altering her primary group 'staff'. Because /projects/alpha is group-owned by alpha with 2770 permissions, group membership grants rwx access, and the setgid bit ensures new files inherit the alpha group. This satisfies the requirement of granting access without changing her primary group.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
usermod -aG alpha jane; usermod -G '' jane; usermod -aG alpha jane
Why it's wrong here
The second command removes all supplementary groups, undoing the first addition. This leaves Jane with only the 'alpha' supplementary group, which is unnecessary and could cause loss of access to other resources.
- ✓
usermod -aG alpha jane
Why this is correct
usermod -aG alpha jane appends jane to the alpha supplementary group without altering her primary group staff, satisfying the constraint. The setgid bit on /projects/alpha then grants group access, letting her list and modify files after re-login.
- ✗
usermod -g alpha jane
Why it's wrong here
Changing the primary group is not required and might break other access controls that depend on the 'staff' group.
- ✗
usermod -G alpha jane
Why it's wrong here
Without the -a flag, this replaces all of Jane's supplementary group memberships with only 'alpha', potentially removing her from other groups she needs.
Go deeper
Related to this question
About these practice questions
This LFCS question is part of Courseiva's 406-question bank — original exam-style content with full explanations and wrong-answer analysis, never real exam questions or exam dumps. Learn why practice questions differ from exam dumps →
JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Linux Foundation exam blueprint
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.