CentOS Stream 9 – Common Problem 093 – Diagnosis and Fix

📖 ~1 min read

Table of contents

1. Symptom & Impact
2. Environment & Reproduction
3. Root Cause Analysis
4. Quick Triage
5. Step-by-Step Diagnosis
6. Solution – Primary Fix
7. Solution – Alternative Approaches
8. Verification & Acceptance Criteria
9. Rollback Plan
10. Prevention & Hardening
11. Related Errors & Cross-Refs
12. References & Further Reading

Symptom & Impact

pam_faillock locks out service accounts on CentOS Stream 9 disrupts services and slows incident response until the root cause is resolved.

Environment & Reproduction

Service account locked out repeatedly because faillock counts failed sudo attempts.

faillock --user 
cat /etc/security/faillock.conf

Root Cause Analysis

Misalignment between auth configuration and CentOS Stream 9 defaults causes the failure path described above.

Quick Triage

Confirm package state, service status, and recent changes before deeper diagnostics.

systemctl status
rpm -qa | grep -i 
journalctl -p err -b --no-pager | tail -100

Step-by-Step Diagnosis

Capture detailed logs, configuration deltas, and runtime state to isolate the failing component.

faillock --user 
grep faillock /etc/pam.d/system-auth /etc/pam.d/password-auth
journalctl -t sudo -n 100

Solution – Primary Fix

Apply the targeted configuration change and restart the relevant services to restore expected behavior.

sudo faillock --user  --reset
sudo authselect select sssd with-faillock --force
sudo sed -i 's/^# deny =.*/deny = 10/' /etc/security/faillock.conf

Solution – Alternative Approaches

Exempt automation accounts via even_deny_root no_magic_root tuning.

Verification & Acceptance Criteria

Validate the fix with deterministic checks and ensure no regressions in dependent services.

faillock --user 
sudo -u  id

Rollback Plan

Revert configuration and restart services to return to the previous known-good state.

authselect select minimal --force
faillock --user  --reset

Prevention & Hardening

Whitelist robotic accounts and monitor faillock counters.

Related Errors & Cross-Refs

Related: faillock, authselect, PAM stack; see also adjacent topics in the CentOS Stream 9 common problems series.

Related tutorial: View the step-by-step tutorial for centos-stream-9.

View all centos-stream-9 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

CentOS Stream documentation, Red Hat upstream guides, and CentOS Stream 9 release notes covering this subsystem.