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.
Make sure that BitLocker is disabled, or find your recovery key.

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 Paint for editing the image.
- If Windows later restores the original boot loader, just reinstall.
- If you wish to change the image or other configuration, just reinstall.
- For advanced settings, edit config.txt before installing. No extra support provided!

Quiet (batch) installation

Edit the config.txt and splash.bmp (or any other images) to your needs.
Run setup.exe batch COMMANDS as administrator, with some of the following commands:
- install – copy the files but don't enable.
- enable-entry – create a new EFI boot entry.
- disable-entry – disable the EFI boot entry.
- enable-bcdedit – use bcdedit to create a new EFI boot entry.
- disable-bootmgr – use bcdedit to disable the EFI boot entry.
- enable-overwrite – overwrite the MS boot loader.
- disable-overwrite – restore the MS boot loader.
- allow-secure-boot – ignore Secure Boot in subsequent commands.
- allow-bitlocker – ignore BitLocker in subsequent commands.
- allow-bad-loader – ignore bad boot loader configuration in subsequent commands.
- disable – run all relevant disable-* commands.
- uninstall – disable and remove completely.
For example, run setup.exe batch install allow-secure-boot enable-overwrite to copy files and overwrite the MS boot loader regardless of Secure Boot status.

Multi-boot configurations

If you only need HackBGRT for Windows:

Run setup.exe, install files without enabling.
Configure your boot loader to start \EFI\HackBGRT\loader.efi.

If you need it for other systems as well:

Configure HackBGRT to start your boot loader (such as systemd-boot): boot=\EFI\systemd\systemd-bootx64.efi.
Run setup.exe, install as a new EFI boot entry.

To install purely on Linux, you can install with setup.exe dry-run and then manually copy files from dry-run/EFI to your [EFI System Partition]/EFI. For further instructions, consult the documentation of your own Linux system.

Configuration

The configuration options are described in config.txt, which the installer copies into [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 installer copies and converts files whose path starts with \EFI\HackBGRT\. For example, to use a file named my.jpg, copy it in the installer folder (same folder as setup.exe) and set the image path in config.txt to path=\EFI\HackBGFT\my.jpg.

If you copy an image file to ESP manually, note that 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.

Advanced users may edit the config.txt to define multiple images, in which case one is picked at random.

Recovery

If something breaks and you can't boot to Windows, you need to use the Windows installation disk (or recovery disk) to fix boot issues.

Building

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

diekmann/HackBGRT