LPIC-2 File Sharing and Samba Practice Question
A Samba server is configured with 'security = ads' and joined to an Active Directory domain. Users can authenticate but cannot access shares. The smb.conf includes 'winbind use default domain = yes'. What could be the problem?
⚠ Common exam trap
Watch out — candidates often assume authentication success means all Samba operations are fine, overlooking the subtle interaction between 'winbind use default domain' and share-level access control parameters like 'valid users'.
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
✓
The 'valid users' parameter uses domain prefix while default domain is set
When 'winbind use default domain = yes' is set, Winbind strips the domain prefix from usernames, so users authenticate as 'username' instead of 'DOMAIN\username'. If the 'valid users' parameter in a share definition explicitly uses the domain prefix (e.g., 'valid users = DOMAIN\username'), the stripped username will not match, and access is denied. This mismatch is the most direct cause of authentication succeeding but share access failing.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The 'winbind use default domain' option should be 'no'
Why it's wrong here
Setting to no would require domain prefix, but the issue is mismatch.
- ✗
The 'idmap backend' is not configured
Why it's wrong here
idmap backend is for UID/GID mapping, not authentication.
- ✗
The Samba server's time is not synchronized with the domain controller
Why it's wrong here
Time sync affects Kerberos but not basic authentication.
- ✓
The 'valid users' parameter uses domain prefix while default domain is set
Why this is correct
If valid users expects 'DOMAIN\user' but winbind strips the domain, authentication fails.
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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.