📖 ~1 min read
Table of contents
Symptom & Impact
Security fixes from new kernel are not active, leaving host exposed and unsupported by policy.
Environment & Reproduction
After unattended updates, manual GRUB edits, or cloud image templates with custom bootloader defaults.
Root Cause Analysis
Default GRUB entry points to older kernel, update incomplete, or reboot did not occur after patching.
Quick Triage
Compare `uname -r` with `rpm -q kernel`, and check current default via `grubby –default-kernel`.
Step-by-Step Diagnosis
Use `grubby –info=ALL`, `awk -F”‘ ‘$1==”menuentry ” {print i++ ” : ” $2}’ /etc/grub2.cfg`, and `journalctl -b -0`.
Solution – Primary Fix
Newest installed kernel is configured as default and matches the running version after reboot.
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Solution – Alternative Approaches
Set correct default kernel with `grubby –set-default`, regenerate GRUB if needed, then reboot in a window.
Verification & Acceptance Criteria
Post-reboot, confirm `uname -r` equals target kernel and platform services start normally.
Rollback Plan
Boot previous kernel from GRUB menu or set earlier entry as default if regression appears.
Prevention & Hardening
Automate reboot compliance checks and alert when running kernel lags installed security baseline.
Related Errors & Cross-Refs
`latest=$(rpm -q kernel –last | awk ‘NR==1{print $1}’ | sed ‘s/kernel-//’); grubby –set-default /boot/vmlinuz-$latest`
Related tutorial: View the step-by-step tutorial for rhel-8.
View all rhel-8 tutorials on the Tutorials Hub →
Browse all common problems & solutions on the Tutorials Hub.
References & Further Reading
RHEL 8 bootloader administration docs and Red Hat guidance for kernel lifecycle management.
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