LPIC-2 System Security Practice Question
A user's SSH public key has been added to '~/.ssh/authorized_keys' on a remote server, but the user is still prompted for a password. Which file permission is most likely causing the issue?
⚠ Common exam trap
Candidates often assume 0600 is too restrictive and pick a more permissive option like 0644 or 0660, not realizing that SSH requires the file to be owned by the user and writable only by that user.
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
✓
0660
SSH's authorized_keys file must have strict permissions to prevent unauthorized modifications. The correct permission is 0600 (owner read/write only) or more restrictive. Permission 0660 (group read/write) is too permissive because it allows group members to modify the file, which SSH interprets as a security risk and falls back to password authentication.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
0660
Why this is correct
Group writable; SSH rejects group-writable authorized_keys.
- ✗
0644
Why it's wrong here
Owner writable, group readable; not group writable, so likely allowed.
- ✗
0444
Why it's wrong here
Read-only for all; no writability, but overly restrictive; might still work.
- ✗
0600
Why it's wrong here
Correct permission, would not cause password prompt.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This LPIC-2 practice question is part of Courseiva's free LPI certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the LPIC-2 exam.