LFCS Essential Commands Practice Question
Exhibit
Refer to the exhibit. $ ls -l /etc/shadow -rw-r----- 1 root shadow 1234 Jan 15 10:00 /etc/shadow $ id uid=1000(user1) gid=1000(user1) groups=1000(user1) $ cat /etc/shadow cat: /etc/shadow: Permission denied
A user with uid 1000 tries to read /etc/shadow and gets 'Permission denied'. The user is not in the shadow group. Which of the following actions would allow the user to read the file without changing the file's group or permissions?
⚠ Common exam trap
Many exam-takers assume ACLs (setfacl) are not a 'permission change' and select option A, but ACLs are indeed a form of permission modification and violate the constraint, while group membership addition is a user attribute change, not a file attribute change.
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
✓
Add user1 to the shadow group using usermod -aG shadow user1
Adding user1 to the shadow group grants group-level read access to /etc/shadow without altering the file's permissions or group ownership. The file is typically owned by root:shadow with permissions 640 (rw-r-----), so members of the shadow group can read it. The usermod -aG command appends the user to the supplementary group, preserving existing group memberships.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Set an ACL using setfacl to grant user1 read access
Why it's wrong here
This would work but is not listed as an option; also it changes the file's ACL, which is not 'without changing file's group or permissions'.
- ✗
Use chmod o+r /etc/shadow as root
Why it's wrong here
This changes permissions, which is not allowed per the question.
- ✓
Add user1 to the shadow group using usermod -aG shadow user1
Why this is correct
Correct: adding to shadow group gives read access via group permission.
- ✗
Change the file owner to user1 using chown
Why it's wrong here
Only root can change ownership.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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