mkgpt: create GPT disk images from partition images

A simple tool for creating disk images with a GPT header and including the contents of provided partition images.

How to build

Just say make followed by sudo make install and you'll most likely be happy. If you want a compact, statically-linked executable instead, install the musl toolchain of your choice (even the musl-gcc wrapper works) and say make static (or CC=whatever make static) followed by sudo make install instead.

How to use

Program options

-o <output_file> specify output filename
--sector-size <size> size of a sector (defaults to 512)
--minimum-image-size <size> minimum size of the image in sectors (defaults to 2048)
--disk-guid <guid> GUID of the entire disk (see GUID format below, defaults to random)
--part <file> <options> begin a partition entry containing the specified image as its data and options as below

Partition options

--name <name> set the name of the entry in the GPT
--type <type> set the type of the entry, either a GUID, numeric MBR-style partition ID, or one of the known partition types
--uuid <guid> specify the UUID of the partition in the GPT (defaults to a random UUID)

Known partition types

EFI system partition: system
BIOS boot partition: bios
FAT types: fat12, fat16, fat16b, fat32, fat16x, fat32x, fat16+, fat32+
NTFS types: ntfs
Linux types: linux, swap

GUID format

GUIDs/UUIDs should be in the canonical representation as per https://en.wikipedia.org/wiki/Universally_unique_identifier#Format without any surrounding braces. An example is: 123E4567-E89B-12D3-A456-426655440000 Optionally, the string random can be used to generate a random GUID.

Why fork?

the original build process seemed bloated for a tool this simple
no way to create swap partitions (borked GUID parsing)
some overly specific code (Linux, Windoze) without a strong need for it
some strange code (static info in oversized, dynamically populated array?)
some rather broken code (required calls in asserts, misaligned pointers, memory leaks)

References

Not enough people seem to know about these things, so here you go:

https://www.drdobbs.com/the-new-c-x-macros/184401387
https://www.embedded.com/reduce-c-language-coding-errors-with-x-macros-part-1/
https://www.embedded.com/reduce-c-language-coding-errors-with-x-macros-part-2/
https://www.embedded.com/reduce-c-language-coding-errors-with-x-macros-part-3/
http://www.catb.org/esr/structure-packing/
https://nullprogram.com/blog/2016/11/22/

Here's some background on the whole GPT mess:

https://en.wikipedia.org/wiki/GUID_Partition_Table
https://en.wikipedia.org/wiki/BIOS_boot_partition (I misunderstood this at first, read if you come from MBR)
Apple's Secrets of the GPT has some useful background (once you ignore the Apple-rific stuff)
https://thestarman.pcministry.com/asm/mbr/GPT.htm (points out disagreements between Windoze protective MBRs and the UEFI specification)

Want to scare yourself?

https://uefi.org/sites/default/files/resources/UEFI_Spec_2_8_final.pdf (enjoy 2,500 pages of dread)

Similar tool with JSON input?

https://gitlab.com/bztsrc/bootboot/tree/master/mkbootimg