The answer is to run chage -M 90 for each existing user. While modifying /etc/login.defs sets default password aging parameters for new accounts and editing /etc/pam.d/common-password enforces minimum length via pam_pwquality, neither change retroactively applies to users already in the system. The chage command directly alters the /etc/shadow file, so executing chage -M 90 for each existing user enforces the 90-day maximum password age policy on them. On the LPIC-2 exam, this tests your understanding that /etc/login.defs only affects future accounts, a common trap where candidates assume configuration files apply universally. A reliable memory tip is that login.defs is for defaults, while chage is for changes—think of it as “defaults for new, chage for old.”
LPIC-2 System Security Practice Question
This LPIC-2 practice question tests your understanding of system security. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 system administrator needs to ensure that all users must change their passwords every 90 days and that passwords must be at least 12 characters long. The administrator modifies /etc/login.defs and /etc/pam.d/common-password. Which additional step is required to enforce these settings for existing users?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "least"
Why it matters: You want the option with minimum overhead, fewest steps, or lowest impact — not the most feature-rich or comprehensive answer.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Run 'chage -M 90' for each existing user
Modifying /etc/login.defs sets default password aging parameters for new users, and /etc/pam.d/common-password enforces password length via pam_pwquality. However, these changes do not retroactively apply to existing users. The chage command modifies the /etc/shadow file directly, and running 'chage -M 90' for each existing user sets their maximum password age to 90 days, enforcing the policy.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Run 'chage -M 90' for each existing user
Why this is correct
chage modifies password aging for existing users.
Clue confirmation
The clue word "least" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Run 'passwd -x 90' for each existing user
Why it's wrong here
passwd -x sets max days but requires the username argument; also less efficient than chage.
✗
Run 'pwconv' to synchronize password aging
Why it's wrong here
pwconv only converts to shadow, it does not set aging.
✗
Run 'pwunconv' then 'pwconv' to update shadow file
Why it's wrong here
This converts shadow passwords but does not set max days.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume modifying /etc/login.defs applies retroactively to existing users, but it only affects future user creations, so a per-user command like chage is required to enforce the policy on current accounts.
Detailed technical explanation
How to think about this question
The /etc/shadow file stores password aging information in fields 4-7 (min days, max days, warn days, inactive days). The chage command directly manipulates these fields, while /etc/login.defs only sets defaults for useradd. In a real-world scenario, a sysadmin might script 'chage -M 90 $(cat /etc/passwd | cut -d: -f1)' to apply the policy to all existing users, but must exclude system accounts to avoid locking them out.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
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. 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
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
System Security — This question tests System Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Run 'chage -M 90' for each existing user — Modifying /etc/login.defs sets default password aging parameters for new users, and /etc/pam.d/common-password enforces password length via pam_pwquality. However, these changes do not retroactively apply to existing users. The chage command modifies the /etc/shadow file directly, and running 'chage -M 90' for each existing user sets their maximum password age to 90 days, enforcing the policy.
What should I do if I get this LPIC-2 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "least". You want the option with minimum overhead, fewest steps, or lowest impact — not the most feature-rich or comprehensive answer.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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