agbsum is a command line utility for patching AGB images.

All AGB images have a header at offsets 0x00-0xE3 (inclusive), of which (29) bytes in 0xA0-0xBD denote metadata.

The first byte after this sequence holds a checksum of the metadata, which if invalid, the device bootloader will usually reject the entire image.

agbsum is written in C99 and uses makefiles as its build system. It has been tested to compile under Clang, GCC, and the Tiny C Compiler (altough the latter may have problems with the standard library). Both GNU Make (gmake) and BSD Make (bmake).

In theory, all “UNIX-like” systems (including older ones) should be supported. Please open a bug report if you experience otherwise.