Ubuntu 24.04 LTS – GRUB does not show newly installed kernel – 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

Installed kernel package is present but missing from GRUB menu entries.

Environment & Reproduction

Appears after kernel updates where grub config generation fails.

uname -r
dpkg -l | grep '^ii  linux-image'
grep menuentry /boot/grub/grub.cfg | head

Root Cause Analysis

grub configuration is stale, wrong boot disk is active, or /boot is not updated correctly.

Quick Triage

Verify installed kernels and check grub-mkconfig output.

ls -1 /boot/vmlinuz-*
sudo update-grub

Step-by-Step Diagnosis

Check boot mode and grub device targets.

[ -d /sys/firmware/efi ] && echo UEFI || echo BIOS
lsblk -f
sudo efibootmgr -v 2>/dev/null || true

Solution – Primary Fix

Regenerate grub config and reinstall bootloader on the active boot disk.

sudo update-grub
sudo grub-install /dev/sda
sudo reboot

Solution – Alternative Approaches

Set explicit saved default to the latest installed kernel entry.

grep menuentry /boot/grub/grub.cfg
sudo grub-set-default 0
sudo update-grub

Verification & Acceptance Criteria

After reboot, system runs expected kernel and GRUB menu lists new entry.

uname -r
grep menuentry /boot/grub/grub.cfg | head -n 20

Rollback Plan

Select previous kernel from Advanced options and pin temporarily.

sudo apt-mark hold linux-image-generic linux-headers-generic

Prevention & Hardening

Monitor kernel postinst hooks and keep /boot capacity healthy.

df -h /boot
ls /etc/kernel/postinst.d

Related Errors & Cross-Refs

Related errors include grub-install warnings and missing initrd references.

Related tutorial: View the step-by-step tutorial for Ubuntu 24.04 LTS.

View all Ubuntu 24.04 LTS tutorials on the Tutorials Hub →

Browse all common problems & solutions on the Tutorials Hub.

References & Further Reading

GRUB documentation and Ubuntu kernel update workflow references.