Re-Bootloader

This project implements a simple AMD64 UEFI bootloader that immediately reboots the system.

Useful as a fall-back disk install in case machines that rely on PXE cannot be configured to auto-retry.

Dependencies

This project requires the following tools and libraries:

• GCC
• GNU-EFI
• Parted
• mtools
• QEMU + OVMF (for running locally)

Installing Dependencies

Ubuntu/Debian:

sudo apt-get install gcc gnu-efi parted mtools qemu-system-x86 ovmf

Fedora/CentOS:

sudo dnf install gcc gnu-efi parted mtools qemu-system-x86 ovmf

Arch Linux:

sudo pacman -S gcc gnu-efi parted mtools qemu ovmf

Building

To build the project, simply run:

make

This will create reboot.efi (the UEFI application) and reboot.img (a disk image containing the bootloader).

Running

To test the bootloader in QEMU, run:

make run

Customization

The Makefile supports several variables that can be overridden:

• INCLUDE_DIRS: Directories to search for header files (default: /usr/lib)
• LD_OBJ: Path to the UEFI crt0 object file (default: /usr/lib/crt0-efi-x86_64.o)
• EFI_LDS: Path to the UEFI linker script (default: /usr/lib/elf_x86_64_efi.lds)
• BIOS_FD: Path to the OVMF BIOS image for QEMU (default: /usr/share/OVMF/FV/OVMF.fd)

Example usage:

make INCLUDE_DIRS="/path/to/efi/headers" LD_OBJ="/path/to/crt0.o"

Writing to a Disk

To write the bootloader image to a physical disk (use with caution!):

sudo dd if=reboot.img of=/dev/sdX bs=4M status=progress

Replace /dev/sdX with the appropriate disk device. Be absolutely certain you're writing to the correct disk, as this will overwrite all existing data.

How it Works

The bootloader is a minimal UEFI application that calls the UEFI firmware's ResetSystem function to immediately reboot the system. The Makefile compiles this application and creates a GPT-formatted disk image containing an EFI System Partition with the bootloader installed.