FreeBSD 15 – expected core dumps are missing due to kern.corefile configuration

📖 ~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

Application crashes occur without generated core files, delaying root-cause analysis.

Environment & Reproduction

Observed after hardening updates that modify limits, sysctl, or filesystem permissions.

ulimit -c
sysctl kern.coredump kern.corefile
loginctl || true

Root Cause Analysis

Core size limits, disabled coredump flag, or unwritable core target directory prevent dump creation.

Quick Triage

Validate process limits and destination path permissions.

limits -e 2>/dev/null || true
ls -ld /var/coredumps
mount | grep coredumps || true

Step-by-Step Diagnosis

Trigger controlled crash test and observe kernel/userland behavior.

sysctl kern.corefile
proccontrol -m coredump -s enable -p $$ || true
kill -ABRT $$

Solution – Primary Fix

Enable coredumps and configure stable writable core path with proper ownership.

sysrc dumpdev='AUTO'
sysctl kern.coredump=1
sysctl kern.corefile='/var/coredumps/%N.%P.core'
mkdir -p /var/coredumps && chmod 700 /var/coredumps

Solution – Alternative Approaches

Use per-service limits in daemon wrapper while keeping global defaults strict.

daemon -u  -o /var/log/.log 

Verification & Acceptance Criteria

Controlled crash generates readable core in target path for debugger analysis.

ls -lh /var/coredumps
file /var/coredumps/*.core | head

Rollback Plan

Revert coredump tuning if storage pressure or compliance conflicts emerge.

sysctl kern.coredump=0
sysctl kern.corefile='core'

Prevention & Hardening

Rotate and age core files with strict retention to avoid disk exhaustion.

find /var/coredumps -type f -mtime +7 -delete

Related Errors & Cross-Refs

Related to read-only datasets, jail restrictions, and process capability controls.

Related tutorial: View the step-by-step tutorial for freebsd-15.

View all freebsd-15 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

FreeBSD core dump handling docs and gdb crash analysis workflows.