🟠 High   ⏱ 5–30 min  Last verified: 19 May 2026
Affected versions: SUSE Linux Enterprise Server 15

📖 ~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

Post-crash analysis is impossible because `/var/crash` contains no vmcore after a panic event.

Environment & Reproduction

Found on SLES 15 hosts with custom crashkernel sizing or NFS dump targets.

Root Cause Analysis

crashkernel reservation is too small or kdump target path is not writable from the kdump initrd.

Quick Triage

Confirm reservation with `cat /proc/cmdline | grep crashkernel`.

Step-by-Step Diagnosis

Inspect `kdump.conf`, `systemctl status kdump`, and run `kexec-tools` self-test.

Illustrative mockup for sles-15 — kdump_no-vmcore-saved_terminal
Terminal diagnostics for kdump fails to write vmcore after kernel panic — Illustrative mockup — Progressive Robot

Solution – Primary Fix

Adjust `crashkernel=auto` to a fixed `crashkernel=512M-:256M` value and rebuild kdump initrd.

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Illustrative mockup for sles-15 — kdump_no-vmcore-saved_logs
Logs and evidence for kdump fails to write vmcore after kernel panic — Illustrative mockup — Progressive Robot

Solution – Alternative Approaches

Switch dump target to a local Btrfs subvolume if network targets are unreliable.

Verification & Acceptance Criteria

A synthetic panic via `echo c > /proc/sysrq-trigger` produces a complete vmcore.

Rollback Plan

Revert kernel parameter changes if reservation breaks memory-sensitive workloads.

Prevention & Hardening

Monitor crashkernel reservation and validate kdump after every kernel update.

Pairs with `kdump: failed to save vmcore` in journal.

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

View all sles-15 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

SUSE kdump and analyzing kernel core documentation.

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