FreeBSD 13 – kernel module fails to load after world/kernel upgrade – Fix & Prevention

📖 ~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

Required drivers fail to load, breaking networking, storage, or security features.

Environment & Reproduction

Typically follows kernel update while third-party modules remain built for old ABI.

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

Root Cause Analysis

Module binary was built against previous kernel and is incompatible with current symbols.

Quick Triage

Confirm kernel/userland version alignment and module build provenance.

uname -a
file /boot/modules/*.ko | head
kldstat

Step-by-Step Diagnosis

Inspect module error messages and ports package versions for kmod dependencies.

kldload -v 
pkg info | grep -i kmod
strings /boot/modules/.ko | grep -i freebsd | head

Solution – Primary Fix

Rebuild or reinstall matching kmod package for active kernel version.

pkg upgrade -y
cd /usr/ports// && make clean install
kldload 

Solution – Alternative Approaches

Boot previous kernel temporarily until matching module package is available.

nextboot -k kernel.old
reboot

Verification & Acceptance Criteria

Module loads cleanly and dependent service starts without warnings.

kldstat | grep 
service  restart
dmesg | grep -i 

Rollback Plan

Unload module and revert boot target if rebuilt module causes instability.

kldunload 
nextboot -k kernel.old

Prevention & Hardening

Coordinate kernel update windows with kmod rebuild automation.

pkg lock  2>/dev/null || true

Related Errors & Cross-Refs

Commonly linked to loader.conf auto-load failures and DKMS-like workflow gaps.

Related tutorial: View the step-by-step tutorial for FreeBSD 13.

View all FreeBSD 13 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

FreeBSD kernel module compatibility and update best practices.