This LPIC-2 practice question tests your understanding of system security. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 security audit reveals that a server with PAM authentication allows users to log in even when the '/etc/nologin' file exists, contrary to policy. Which PAM module is most likely misconfigured or missing?
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.
pam_nologin.so
Denies login if /etc/nologin exists.
pam_securetty.so
Why wrong: Controls root TTY access, not /etc/nologin.
pam_access.so
Why wrong: Controls access based on /etc/security/access.conf.
pam_lastlog.so
Why wrong: Records last login time, no denial.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
pam_nologin.so
Option B is correct because pam_nologin.so checks for /etc/nologin and denies login if present. Option A is wrong because pam_securetty.so restricts root login on ttys, unrelated. Option C is wrong because pam_lastlog.so records login time. Option D is wrong because pam_access.so restricts based on access lists, not nologin.
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
For each option: why learners choose it and why it is or isn't the right answer here.
pam_nologin.so
Why this is correct
Denies login if /etc/nologin exists.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Standard ACLs match source addresses.
pam_securetty.so
Why it's wrong here
Controls root TTY access, not /etc/nologin.
pam_access.so
Why it's wrong here
Controls access based on /etc/security/access.conf.
pam_lastlog.so
Why it's wrong here
Records last login time, no denial.
Common exam traps
ACLs are processed top to bottom. The first matching entry wins, and an implicit deny usually exists at the end.
Detailed technical explanation
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.
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
A practitioner preparing for the LPIC-2 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. 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 exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
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 LPIC-2 ACL questions on filtering logic and placement.
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FAQ
System Security — This question tests System Security — Standard ACLs match source addresses..
The correct answer is: pam_nologin.so — Option B is correct because pam_nologin.so checks for /etc/nologin and denies login if present. Option A is wrong because pam_securetty.so restricts root login on ttys, unrelated. Option C is wrong because pam_lastlog.so records login time. Option D is wrong because pam_access.so restricts based on access lists, not nologin.
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 LPIC-2 ACL questions on filtering logic and placement.
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Standard ACLs match source addresses.
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Last reviewed: Jun 24, 2026
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