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GRUB Repair Guide

Add Missing Windows 11 Entry (Tested on Debian 12 + Windows 11 UEFI systems)

Basic Fix (90% Success Rate)

sudo apt install os-prober
sudo update-grub

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

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