🔴 Critical   ⏱ 5–30 min  Last verified: 19 May 2026
Affected versions: FreeBSD 13

📖 ~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

Host panics or fails to boot because kernel and loadable modules are from different build sets.

Environment & Reproduction

Seen after partial update or interrupted merge of /etc during upgrade.

freebsd-version -kru
kldstat

Root Cause Analysis

Kernel binary and modules in /boot/kernel are out of sync after incomplete update steps.

Quick Triage

Compare running kernel version with userland and module versions.

uname -a
freebsd-version -kru

Step-by-Step Diagnosis

Review update history and detect partial install state.

ls -lah /var/db/freebsd-update
tail -n 200 /var/log/messages
Illustrative mockup for freebsd-13 — kernel_module_panic
Kernel panic from module mismatch — Illustrative mockup — Progressive Robot

Solution – Primary Fix

Complete pending update install phases and reboot into consistent kernel set.

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freebsd-update install
shutdown -r now
freebsd-update install
Illustrative mockup for freebsd-13 — kernel_module_fixed
Kernel and module set aligned — Illustrative mockup — Progressive Robot

Solution – Alternative Approaches

Boot previous boot environment or previous kernel from loader menu for recovery.

Verification & Acceptance Criteria

Kernel and userland versions report expected alignment.

freebsd-version -kru

Rollback Plan

Return to previously known-good boot environment while re-validating update sequence.

Prevention & Hardening

Perform upgrades in controlled windows and document required multi-step install/reboot order.

link_elf_obj: symbol not found, KLD mismatch, panic in module load path.

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-update handbook and kernel update best practices.

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