Boot Loader Variables Not Persisting Across Reboot

📖 ~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

Kernel and loader tunables may not persist when edits are made to the wrong file or syntax is invalid.

Environment & Reproduction

Expected tunables are absent after reboot and module auto-load behavior is inconsistent.

Root Cause Analysis

Systems using UEFI or BIOS loader with custom tuning in loader.conf or loader.conf.local.

Quick Triage

Root permissions and backup of existing /boot configuration files.

Step-by-Step Diagnosis

[image_ref: 0] Run sysctl -a | grep tunable_name; grep -n tunable_name /boot/loader.conf*; dmesg | grep -i loader.

Solution – Primary Fix

[image_ref: 1] Ensure tunables are in /boot/loader.conf with proper quoted syntax and no duplicate conflicting entries.

Solution – Alternative Approaches

Move misplaced settings from rc.conf to loader.conf where appropriate, correct syntax, and reboot to apply boot-time variables.

Verification & Acceptance Criteria

After reboot, sysctl values and module load state match intended boot configuration.

Rollback Plan

Restore previous loader files from backup if system behavior regresses after tuning.

Prevention & Hardening

Track boot tunables in change control and separate runtime sysctl from loader-only settings.

Related Errors & Cross-Refs

Escalate if boot loader corruption or filesystem issues prevent reading loader configuration.

Related tutorial: View the step-by-step tutorial for freebsd-14.

View all freebsd-14 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

loader.conf(5), loader(8), sysctl(8), FreeBSD boot process documentation.