LPIC-1 Administrative Tasks Practice Question
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?
⚠ Common exam trap
A common mix-up: candidates confuse 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.
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
✓
password required pam_pwhistory.so remember=5
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.
Answer analysis
Option-by-option breakdown
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
Incorrect. The 'optional' control flag means the module's success is not required; thus, password history may not be enforced.
- ✗
password sufficient pam_pwhistory.so remember=5
Why it's wrong here
Incorrect. The 'sufficient' control flag means if this module succeeds, the password change is considered successful, but if it fails, the history check may be bypassed, so it does not reliably enforce password history.
- ✓
password required pam_pwhistory.so remember=5
Why this is correct
Correct. The 'required' control flag ensures the module must succeed for the password change to proceed, and 'remember=5' enforces that the last 5 passwords cannot be reused.
- ✗
password requisite pam_pwhistory.so remember=5
Why it's wrong here
The 'requisite' control flag causes immediate failure if the module fails, but this is not the standard choice for password history; 'required' is preferred as it allows other modules to execute even if pam_pwhistory fails, providing better fault tolerance and consistency with common PAM configurations.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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