This LPIC-1 practice question tests your understanding of administrative tasks. 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.
An administrator wants to enforce a password history that prevents using the last 5 passwords. Which directive should be added to /etc/pam.d/system-auth?
password optional pam_pwhistory.so remember=5
Why wrong: 'optional' means it can be ignored.
password sufficient pam_pwhistory.so remember=5
Why wrong: 'sufficient' would not enforce if other modules succeed.
password required pam_pwhistory.so remember=5
Correct: enforces password history of 5 passwords.
password requisite pam_pwhistory.so remember=5
Why wrong: 'requisite' is not typical for password history.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
password required pam_pwhistory.so remember=5
Option C is correct because the `required` control flag ensures that the `pam_pwhistory.so` module must succeed for the password change to proceed, and `remember=5` enforces that the last 5 passwords cannot be reused. This is the standard way to enforce password history in PAM (Pluggable Authentication Modules) on Linux systems.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
password optional pam_pwhistory.so remember=5
Why it's wrong here
'optional' means it can be ignored.
password sufficient pam_pwhistory.so remember=5
Why it's wrong here
'sufficient' would not enforce if other modules succeed.
password required pam_pwhistory.so remember=5
Why this is correct
Correct: enforces password history of 5 passwords.
Related concept
Read the scenario before looking for a memorised answer.
password requisite pam_pwhistory.so remember=5
Why it's wrong here
'requisite' is not typical for password history.
Common exam traps
The trap here is confusing the PAM control flags (`required`, `requisite`, `sufficient`, `optional`) and their specific behaviors, especially thinking `requisite` is equivalent to `required` for password history, when in fact `required` is the standard choice for this module.
Detailed technical explanation
The `pam_pwhistory.so` module stores hashed copies of previous passwords in a file (often `/etc/security/opasswd`) and compares new passwords against that history. The `remember=N` parameter specifies how many previous passwords to track; the module uses a rolling list, so after N changes, the oldest password is dropped. In a real-world scenario, combining this with `pam_cracklib.so` or `pam_pwquality.so` ensures both complexity and history are enforced.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A practitioner preparing for the LPIC-1 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. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
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FAQ
Administrative Tasks — This question tests Administrative Tasks — Read the scenario before looking for a memorised answer..
The correct answer is: password required pam_pwhistory.so remember=5 — Option C is correct because the `required` control flag ensures that the `pam_pwhistory.so` module must succeed for the password change to proceed, and `remember=5` enforces that the last 5 passwords cannot be reused. This is the standard way to enforce password history in PAM (Pluggable Authentication Modules) on Linux systems.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 25, 2026
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