Booting an old kernel is a rollback tactic, not a permanent fix. Remove or pin broken kernel packages after confirming a stable boot. Keep at least one known-good kernel installed.
What you will achieve
Select a previous Linux kernel from the GRUB menu on Ubuntu or Debian when a kernel update causes boot failure, driver regression, or panic — then stabilise default boot behaviour.
1) Access GRUB at boot
Reboot and hold Shift (BIOS) or tap Esc (UEFI) during firmware splash to show the GRUB menu. On dual-boot setups, the menu may appear automatically. If hidden, edit /etc/default/grub:
GRUB_TIMEOUT_STYLE=menu
GRUB_TIMEOUT=5Then run sudo update-grub.
2) Choose Advanced options
Select Advanced options for Ubuntu (or Debian). You will see multiple entries per kernel version:
Ubuntu, with Linux 6.8.0-XX-generic— normal boot... (recovery mode)— single-user troubleshooting
Pick the previous working kernel version — one increment behind the latest is usually right.
3) Confirm boot success
uname -r
dpkg -l 'linux-image-*' | grep iiRunning kernel should match your GRUB selection. Test hardware that broke (Wi‑Fi, NVIDIA, ZFS) before declaring victory.
4) Pin default kernel temporarily
grep 'menuentry' /boot/grub/grub.cfg | head -10Note the menu entry title. Set default in /etc/default/grub by index or saved entry:
GRUB_DEFAULT="Advanced options for Ubuntu>Ubuntu, with Linux 6.5.0-XX-generic"
sudo update-grubAlternatively use GRUB_SAVEDEFAULT=true and grub-set-default after one successful manual boot.
5) Hold or remove bad kernel (after rollback works)
sudo apt-mark hold linux-image-6.8.0-XX-generic
# or once stable:
sudo apt purge linux-image-6.8.0-XX-genericNever purge the kernel you are currently running. Remove newest broken one only after confirming old kernel boots reliably.
6) Rebuild initramfs if modules missing
sudo update-initramfs -u -k all
sudo update-grubNeeded when rollback shows mount errors or missing disk drivers — rare on stock Ubuntu but common with custom modules.
7) Document and report
If a specific kernel version breaks your hardware, file a bug against the linux package with ubuntu-bug linux on Ubuntu. Include dmesg from failed boot and note which previous kernel works — helps maintainers revert bad patches faster.
Verify
uname -r
sudo reboot # should land on chosen defaultSystem reaches login or SSH. Document kernel version and bug (e.g. broken NVIDIA module) for later proper fix or bug report.