📖 ~1 min read
Table of contents
Symptom & Impact
User login fails despite correct credentials, preventing normal access.
Environment & Reproduction
Debian 9 PAM and account policy changed during security updates.
Root Cause Analysis
PAM module order or account restrictions reject valid authentication.
Quick Triage
Inspect auth logs and account lock or expiry state before resets.
Step-by-Step Diagnosis
Audit PAM chain, shell assignment, and password policy enforcement.
Solution – Primary Fix
Correct PAM ordering, unlock account, and apply compliant policy settings.
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Solution – Alternative Approaches
Provide temporary break-glass console access via approved process.
Verification & Acceptance Criteria
User authentication succeeds and session initialization is complete.
Rollback Plan
Restore previous PAM files and account attributes from backup.
Prevention & Hardening
Stage PAM changes and simulate lockout impacts before rollout.
Related Errors & Cross-Refs
Connected to SSH auth denials and password expiry policy issues.
Related tutorial: View the step-by-step tutorial for debian-9.
View all debian-9 tutorials on the Tutorials Hub →
Browse all common problems & solutions on the Tutorials Hub.
References & Further Reading
Linux PAM administration and Debian account security references.
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