📖 ~1 min read
Table of contents
Symptom & Impact
After upgrade and reboot, system still runs an older kernel.
Environment & Reproduction
Can happen when GRUB default is pinned or config is not regenerated.
Root Cause Analysis
Bootloader entry selection points to outdated kernel image.
Quick Triage
Compare `uname -r` with installed kernel packages from `dpkg -l | grep linux-image`.
Step-by-Step Diagnosis
Inspect `/boot/grub/grub.cfg` entries and `GRUB_DEFAULT` behavior before rebooting again.
Solution – Primary Fix
Regenerate boot menu using `sudo update-grub` and set correct default kernel entry.
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Solution – Alternative Approaches
Use GRUB saved entry mode for controlled kernel pinning.
Verification & Acceptance Criteria
Post-reboot kernel version matches intended latest package.
Rollback Plan
Boot prior kernel from GRUB advanced options if regression occurs.
Prevention & Hardening
Validate running kernel in post-maintenance checks.
Related Errors & Cross-Refs
Related to DKMS failures and initramfs generation issues.
Related tutorial: View the step-by-step tutorial for debian-12.
View all debian-12 tutorials on the Tutorials Hub →
Browse all common problems & solutions on the Tutorials Hub.
References & Further Reading
Debian Bookworm kernel and GRUB administration docs.
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