Kernel Update Installed but Old Kernel Keeps Booting

📖 ~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

yum installs new kernel packages but reboot continues with an older kernel.

Environment & Reproduction

uname -r does not match latest installed kernel version.

Root Cause Analysis

GRUB default entry, pinned kernel settings, or failed post-install script.

Quick Triage

List installed kernels and inspect GRUB default index.

Step-by-Step Diagnosis

Run rpm -qa kernel, grub2-editenv list, grub2-mkconfig checks, systemctl status, and journalctl -b -1.

Solution – Primary Fix

Set correct default kernel with grub2-set-default, rebuild config if needed, ensure boot service integrity, and reboot.

Solution – Alternative Approaches

uname -r matches target kernel and core services start cleanly.

Verification & Acceptance Criteria

Select previous kernel from GRUB menu if compatibility issues appear.

Rollback Plan

Verify boot target in maintenance runbooks after each kernel yum update.

Prevention & Hardening

Add post-reboot checks that compare installed and running kernel versions.

Related Errors & Cross-Refs

Custom GRUB policies are common on long-lived RHEL 7 estates.

Related tutorial: View the step-by-step tutorial for rhel-7.

View all rhel-7 tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

Escalate if bootloader corruption or firmware interaction is suspected.