RHEL 10 – New kernel installed but old kernel still boots by default – 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

After updates, system continues booting an older kernel, missing bug and security fixes.

Environment & Reproduction

Occurs with custom grub defaults or stale BLS entries.

uname -r
rpm -q kernel
grubby --default-kernel

Root Cause Analysis

Bootloader default points to legacy entry or failed post-transaction script did not update selection.

Quick Triage

Compare running kernel with installed newest package.

rpm -q --last kernel | head -n 3
grubby --info=ALL | grep -E 'index=|kernel='
journalctl -b -0 -n 20 --no-pager

Step-by-Step Diagnosis

Review grub environment and BLS entries.

grub2-editenv list
ls -1 /boot/loader/entries
cat /etc/default/grub

Solution – Primary Fix

Set newest kernel explicitly and regenerate config where required.

NEWK=$(rpm -q --qf '%{VERSION}-%{RELEASE}.%{ARCH}
' kernel | sort -V | tail -1)
sudo grubby --set-default /boot/vmlinuz-${NEWK}
grubby --default-kernel

Solution – Alternative Approaches

Set saved entry by title and verify after reboot windows.

sudo grub2-set-default 0
sudo grub2-editenv list

Verification & Acceptance Criteria

System boots expected kernel on next restart.

reboot
uname -r
grubby --default-kernel

Rollback Plan

Switch default back if workload compatibility issues appear.

sudo grubby --set-default /boot/vmlinuz-
reboot

Prevention & Hardening

Audit kernel default after each patch cycle and keep one known-good fallback installed.

dnf updateinfo list security
rpm -q kernel

Related Errors & Cross-Refs

Related to broken initramfs generation and custom grub scripts overriding BLS behavior.

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 bootloader and kernel lifecycle documentation for BLS and grub management.