RHEL 10 – kdump does not capture vmcore on panic because crashkernel is mis-sized – 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

Kernel panics do not produce vmcore files, preventing low-level root cause analysis.

Environment & Reproduction

Common on memory-constrained systems or after kernel upgrades.

systemctl status kdump
cat /proc/cmdline

Root Cause Analysis

Reserved crashkernel memory is insufficient or missing for current kernel footprint.

Quick Triage

Verify kdump service, command line args, and target path readiness.

systemctl status kdump
grep crashkernel /proc/cmdline
journalctl -u kdump -n 80 --no-pager
getenforce
firewall-cmd --state

Step-by-Step Diagnosis

Inspect loaded kexec image and estimate memory reservation needs.

kdumpctl showmem
kdumpctl status
ls -l /var/crash

Solution – Primary Fix

Set appropriate crashkernel value, rebuild boot config, and restart kdump.

sudo grubby --update-kernel=ALL --args='crashkernel=1G'
sudo reboot
sudo systemctl enable --now kdump
sudo kdumpctl restart

Solution – Alternative Approaches

Offload vmcore to remote NFS/SSH target if local crash partition is limited.

sudo sed -i 's|^#path .*|path /var/crash|' /etc/kdump.conf
sudo systemctl restart kdump

Verification & Acceptance Criteria

Panic test captures vmcore and kdump logs show successful save sequence.

kdumpctl test
ls -lh /var/crash
journalctl -u kdump -n 100 --no-pager

Rollback Plan

Remove crashkernel override and restore previous boot args.

sudo grubby --update-kernel=ALL --remove-args='crashkernel=1G'
sudo reboot

Prevention & Hardening

Revalidate kdump memory settings after each kernel lifecycle update.

Automate patch management and compliance across your fleet with our DevOps services.

kdumpctl status
uname -r

Related Errors & Cross-Refs

Related to secure boot kexec restrictions and full /var/crash partitions.

Related tutorial: View the step-by-step tutorial for rhel-10.

View all rhel-10 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

RHEL kdump administration and vmcore analysis documentation.