isobemak 0.1.0

Create bootable ISO images with FAT32 and UEFI (El Torito) support in Rust.
Documentation

isobemak is a Rust crate designed to create bootable disk images. It's built for generating an ISO file that contains a FAT32 filesystem, tailored for UEFI booting.

How it works

The crate handles two main tasks to produce a bootable ISO:

  1. Creating a FAT32 Disk Image: It creates a new file, sizes it to 32 MiB, and formats it as FAT32. The crate then copies two essential files, a bootloader and a kernel, into the EFI/BOOT/ directory inside this image. It renames the bootloader to BOOTX64.EFI and the kernel to KERNEL.EFI, a standard convention for UEFI booting.

  2. Generating the ISO File: The crate creates a new ISO file and populates it with the necessary data structures to make it bootable according to the El Torito standard. This includes:

    • A Primary Volume Descriptor with information like the volume ID "FULLERENE" and the total number of sectors.
    • A Boot Record Volume Descriptor that identifies the image as an El Torito bootable specification.
    • A Boot Catalog which specifies the location and size of the boot image.

The FAT32 disk image created in the first step is then added to the ISO at a specific location (LBA 20), making it the bootable payload for the ISO.

Project Structure

  • src/lib.rs: The main entry point that coordinates the creation of both the FAT32 image and the final ISO file.
  • src/fat32.rs: Contains the logic for creating and formatting the 32 MiB FAT32 disk image and copying the bootloader and kernel files into it.
  • src/iso.rs: Handles the creation of the ISO9660 filesystem with El Torito bootable extensions. It sets up the various volume descriptors and the boot catalog.
  • src/utils.rs: Provides utility functions, such as pad_sector, which aligns files to the correct sector size (2048 bytes).

Usage

The create_disk_and_iso function in src/lib.rs is the primary function to be used. It takes the paths for the output FAT32 and ISO images, as well as file handles for the bootloader and the kernel.

pub fn create_disk_and_iso(
    fat32_img: &Path,
    iso: &Path,
    bellows: &mut File,
    kernel: &mut File,
) -> io::Result<()>