RTFM · Troubleshooting
GRUB install and recovery
Installing GRUB correctly the first time, rebuilding config safely, and recovering a machine whose bootloader is gone.
Correct initial install
Install GRUB onto the disk whose partition table the firmware reads, not into a partition. BIOS and UEFI differ mechanically.
# UEFI systems
grub-install --target=x86_64-efi --efi-directory=/boot/efi --bootloader-id=saphira
# Legacy BIOS
grub-install /dev/sda
# Both: regenerate config afterwards
grub-mkconfig -o /boot/grub/grub.cfgAfter kernel changes
Any manually installed kernel needs corresponding GRUB awareness. Re-run grub-mkconfig yourself as habit.
grub-mkconfig detects kernels under /boot and generates entries including fallback ones. Running it takes seconds; forgetting it ruins mornings.
Broken beyond local repair
Boot rescue media, chroot, then grub-install fresh. Modern UEFI machines additionally benefit from efibootmgr inspection:
efibootmgr # list NVRAM entries
efibootmgr -c -d /dev/sda -p 1 -L saphira -l '\EFI\saphira\grubx64.efi'Prove it works: survive the next reboot
intentional reboot right after any bootloader work, performed while you still remember what changed.
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