sudo apt install os-prober
sudo update-grub

sudo lsblk -o NAME,FSTYPE,SIZE,MOUNTPOINT

Look for:

• FAT32 partition (usually 100-500MB)
• Example output: nvme0n1p1 vfat 100M /boot/efi

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
}

sudo update-grub
sudo reboot

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”

1. Replace hd0 with actual disk number
2. Use lsblk to confirm partition numbers

No bootmgfw.efi

1. Check Windows installation mode (must be UEFI)
2. Disable “Secure Boot”

GRUB menu not showing

1. Hold Shift during boot
2. Run sudo grub-install /dev/nvme0n1