This LFCS practice question tests your understanding of user and group management. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A user reports that they cannot log in via SSH. The system administrator checks that the account is not locked, the password is correct, and the shell is valid. However, the user's home directory is owned by root instead of the user. What is the most likely cause of the login failure?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The home directory ownership is incorrect, causing SSH PAM session module to reject login
Option D is correct because SSH uses PAM, and the pam_unix module checks that the home directory is owned by the user and not writable by others. If owned by root, SSH may deny login for security reasons. Option A (shadow file) would be different if permission wrong. Option B (nologin) would affect all users. Option C (shell not in /etc/shells) would give a different error.
Key principle: ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
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 home directory ownership is incorrect, causing SSH PAM session module to reject login
Why this is correct
pam_umask or pam_limits may check ownership; many systems require home owned by user.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Standard ACLs match source addresses.
✗
The user's login shell is not listed in /etc/shells
Why it's wrong here
This error typically shows 'shell not in /etc/shells' during login attempt.
✗
The /etc/nologin file exists
Why it's wrong here
/etc/nologin prevents all non-root logins; would affect all users.
✗
The user's entry in /etc/shadow is corrupted
Why it's wrong here
Corrupted shadow would cause password authentication failure, not ownership issue.
Common exam traps
Common exam trap: ACLs stop at the first match
ACLs are processed top to bottom. The first matching entry wins, and an implicit deny usually exists at the end.
Trap categories for this question
Command / output trap
This error typically shows 'shell not in /etc/shells' during login attempt.
Detailed technical explanation
How to think about this question
ACL questions test precision: source, destination, protocol, port and direction. A generally correct ACL can still fail if it is applied on the wrong interface or in the wrong direction.
KKey Concepts to Remember
Standard ACLs match source addresses.
Extended ACLs can match source, destination, protocol and ports.
The first matching ACL entry is used.
There is usually an implicit deny at the end.
TExam Day Tips
→Check inbound versus outbound direction.
→Read the ACL from top to bottom.
→Look for a broader permit or deny above the intended line.
Key takeaway
ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
Real-world example
How this comes up in practice
A security administrator must allow nursing staff to reach a patient records server while blocking access from the guest Wi-Fi VLAN. After applying an extended ACL, traffic is still blocked from nursing workstations. The ACL was applied outbound instead of inbound on the wrong interface. Questions like this test ACL direction and placement rules.
What to study next
Got this wrong? Here's your next step.
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related LFCS ACL questions on filtering logic and placement.
User and Group Management — This question tests User and Group Management — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: The home directory ownership is incorrect, causing SSH PAM session module to reject login — Option D is correct because SSH uses PAM, and the pam_unix module checks that the home directory is owned by the user and not writable by others. If owned by root, SSH may deny login for security reasons. Option A (shadow file) would be different if permission wrong. Option B (nologin) would affect all users. Option C (shell not in /etc/shells) would give a different error.
What should I do if I get this LFCS question wrong?
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related LFCS ACL questions on filtering logic and placement.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Standard ACLs match source addresses.
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