Restore Efi

To repair the EFI (Extensible Firmware Interface) system partition on a drive, you’ll typically need a live Linux or Windows recovery environment, depending on your operating system. Below are step-by-step guides for both Windows and Linux systems.

🪟 For Windows Systems

🔧 Requirements:

Windows installation media (USB/DVD)
Admin access to recovery environment

✅ Steps:

Boot into Windows Recovery Environment (WinRE):
- Boot from Windows installation media.
- Choose your language, then click “Repair your computer”.
- Select Troubleshoot > Advanced Options > Command Prompt.

Find your EFI partition:

diskpart
list disk
select disk 0             # (or your OS drive)
list partition
select partition X        # (usually ~100MB, type: EFI)
assign letter=s
exit

Rebuild the EFI boot files:
- Run this from the command prompt:
```
bcdboot C:\Windows /s S: /f UEFI
```
- This copies boot files to the EFI system partition and recreates the BCD store.
Reboot:
```
exit
```
Remove installation media and reboot your system.

🐧 For Linux Systems (e.g., GRUB on Ubuntu/Debian)

🔧 Requirements:

Live USB of your Linux distro
Root access in chroot environment

✅ Steps:

Boot into Live USB and open a terminal.
Identify partitions:
```
sudo fdisk -l
```
- Note your EFI partition (usually /dev/sdX1, FAT32, ~100–500MB)
- Note your Linux root partition (e.g., /dev/sdX2)

Mount and chroot into your system:

sudo mount /dev/sdX2 /mnt
sudo mount /dev/sdX1 /mnt/boot/efi
sudo mount --bind /dev /mnt/dev
sudo mount --bind /proc /mnt/proc
sudo mount --bind /sys /mnt/sys
sudo chroot /mnt

Reinstall GRUB and update config:

grub-install --target=x86_64-efi --efi-directory=/boot/efi --bootloader-id=GRUB
update-grub

Exit and reboot:
```
exit
sudo umount -R /mnt
sudo reboot
```

🧠 Notes:

Make sure UEFI is enabled in BIOS settings.
On Windows, bcdboot repairs both the BCD and EFI files.
On Linux, grub-install + update-grub restores bootloader in EFI.