Unsigned Kernel Module Refused Under Secure Boot

📖 ~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

Third-party kernel module fails to load with signature or key rejection errors.

Environment & Reproduction

Run `mokutil –sb-state`, `modprobe `, and inspect `dmesg` for signature failures.

Root Cause Analysis

Confirm `kmod`, kernel-devel, and signing toolchain packages match running kernel.

Quick Triage

If module is loaded via service, review unit startup dependency and error handling.

Step-by-Step Diagnosis

Use `journalctl -k -b` to capture module verification messages during boot and runtime.

Solution – Primary Fix

Capture module build config, key fingerprints, and enrolled MOK list before changes.

Solution – Alternative Approaches

Not a network-root cause, but ensure remote recovery access while testing module load paths.

Verification & Acceptance Criteria

Validate module and helper script contexts if files were copied from nonstandard locations.

Rollback Plan

Sign module with trusted key, enroll MOK if needed, then reload module and dependent services.

Prevention & Hardening

Confirm module loads cleanly and required hardware or feature path becomes operational.

Related Errors & Cross-Refs

Integrate module signing into CI for every kernel update cycle.

Related tutorial: View the step-by-step tutorial for rhel-9.

View all rhel-9 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

Provide kernel build info, signing commands, and boot-time verification logs.