GRUB Repair Guide
Add Missing Windows 11 Entry (Tested on Debian 12 + Windows 11 UEFI systems)
1. Basic Fix (90% Success Rate)
sudo apt install os-prober sudo update-grub
2. Manual GRUB Entry (For NVMe Drivers)
a. Identify Windows EFI Partition
sudo lsblk -o NAME,FSTYPE,SIZE,MOUNTPOINT
Look for:
- FAT32 partition (usually 100-500MB)
- Example output: nvme0n1p1 vfat 100M /boot/efi
b. Create Custom Entry
sudo nano /etc/grubd/40_custom
Add:
menuentry "Windows 11" { insmod part_gpt insmod chain insmod ntfs set root=(hd0,gpt1) #hd0 = first disk, gpt1 = first partition chainloader /EFI/Microsoft/Boot/bootmgfw/efi }
c. Apply Changes
sudo update-grub sudo reboot
3. Verify UEFI Mode
Linux should show UEFI vars:
ls /sys/firmware/efi/efivars
Windows partition should have EFI files:
sudo ls /boot/efi/EFI/Microsoft/Boot
Expected file is bootmgfw.efi
Troubleshooting Table
“hd0 not found”
- Replace hd0 with actual disk number
- Use lsblk to confirm partition numbers
No bootmgfw.efi
- Check Windows installation mode (must be UEFI)
- Disable “Secure Boot”
GRUB menu not showing
- Hold Shift during boot
- Run sudo grub-install /dev/nvme0n1