HackBGRT

HackBGRT is intended as a boot logo changer for UEFI-based Windows systems.

Summary

When booting on a UEFI-based computer, Windows may show a vendor-defined logo which is stored on the UEFI firmware in a section called Boot Graphics Resource Table (BGRT). It's usually very difficult to change the image permanently, but a custom UEFI application may be used to overwrite it during the boot. HackBGRT does exactly that.

Usage

Important: If you mess up the installation, your system may become unbootable! Create a rescue disk before use. This software comes with no warranty. Use at your own risk.

• Make sure that your computer is booting with UEFI.
• Make sure that Secure Boot is disabled, unless you know how to sign EFI applications.

Windows installation

• Get the latest release from the Releases page.
• Start setup.exe and follow the instructions.
  • You may need to manually disable Secure Boot and then retry.
  • The installer will launch Notepad for modifying the configuration.
    • If you need only one custom image, the defaults are fine.
    • Otherwise, check out the examples in the configuration file.
  • The installer will launch Paint for creating the image(s).
    • You can create multiple images by using Save As.
    • Be sure to always use the 24-bit BMP/DIB format.
  • If Windows later restores the original boot loader, just reinstall.
  • If you wish to change the image or other configuration, just reinstall.

Multi-boot configurations

If you only need HackBGRT for Windows:

• Extract the latest release to [EFI System Partition]\EFI\HackBGRT\.
• Set boot=\EFI\Microsoft\Boot\bootmgfw.efi in config.txt.
• Point your boot loader to \EFI\HackBGRT\bootx64.efi.

If you need it for other systems as well:

• Extract the latest release to [EFI System Partition]\EFI\HackBGRT\.
• Set boot=\EFI\your-actual-boot-loader.efi in config.txt.
• Set \EFI\HackBGRT\bootx64.efi as your default boot loader with efibootmgr or some other EFI boot manager tool.

On 32-bit machines, use bootia32.efi instead of bootx64.efi.

Configuration

The configuration options are described in config.txt, which should be stored in [EFI System Partition]\EFI\HackBGRT\config.txt.

Images

The image path can be changed in the configuration file. The default path is [EFI System Partition]\EFI\HackBGRT\splash.bmp.

The image must be a 24-bit BMP file with a 54-byte header. That's a TrueColor BMP3 in Imagemagick, or 24-bit BMP/DIB in Microsoft Paint.

Multiple images may be specified, in which case one is picked at random.

Recovery

If something breaks and you can't boot to Windows, you have the following options:

• Windows installation (or recovery) media can fix boot issues.
• You can copy [EFI System Partition]\EFI\HackBGRT\bootmgfw-original.efi into [EFI System Partition]\EFI\Microsoft\Boot\bootmgfw.efi by some other means such as Linux or Windows command prompt.

Building

• Compiler: GCC targeting w64-mingw32
• Compiler flags: see Makefile
• Libraries: gnu-efi