FreeBSD 12 – Common Problem 020 – Kernel Module Fails to Load After Update

📖 ~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

Features depending on module fail, sometimes blocking storage/network functionality.

Environment & Reproduction

Occurs after `freebsd-update` when third-party modules were built for prior patch level.

Root Cause Analysis

Module ABI version mismatch between running kernel and installed `.ko` file.

Quick Triage

Inspect kernel and module load errors.

freebsd-version -kru
kldstat
dmesg | tail -n 80

Step-by-Step Diagnosis

Attempt manual load and capture exact mismatch message.

kldload if_bridge
file /boot/modules/*.ko | head
strings /boot/modules/yourmodule.ko | grep -i freebsd

Solution – Primary Fix

Rebuild/reinstall module for current kernel and reboot if required.

pkg upgrade -y
portsnap fetch update
make -C /usr/ports/your/module clean install

Solution – Alternative Approaches

Boot previous kernel from loader menu temporarily while compatible module is prepared.

Verification & Acceptance Criteria

Module loads cleanly and dependent service starts without errors.

Rollback Plan

Unload new module and restore prior kernel environment if regression appears.

Prevention & Hardening

Pin update workflow to rebuild out-of-tree modules in same maintenance window.

Related Errors & Cross-Refs

`linker_load_file: unsupported file type`, `Exec format error`, unresolved symbols.

Related tutorial: View the step-by-step tutorial for freebsd-12.

View all freebsd-12 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

`kldload(8)`, `kldstat(8)`, FreeBSD update procedures.