geteltorito

geteltorito [OPTIONS] <ISO_IMAGE>

-o <output_file>
    Specifies the path for the output file where the extracted boot image will be saved. If omitted, the output is directed to standard output (stdout).

-a
    Extracts all boot images found within the specified ISO. Each image will be named based on a pattern (e.g., boot.img.0, boot.img.1).

-i <image_number>
    Selects a specific boot image to extract when multiple are present in the ISO. Image numbers typically start from 0.

-h, --help
    Displays a brief help message and exits.

-v, --version
    Displays the program's version information and exits.

geteltorito is a specialized utility designed to extract the bootable El Torito image from an ISO 9660 or UDF CD/DVD image. The El Torito specification defines how a CD-ROM can be made bootable, often mimicking a floppy disk, hard disk, or a non-emulated boot sector. This tool is invaluable when you need to create a bootable USB drive from a CD/DVD ISO image, or when you wish to analyze or manipulate the boot image itself. It can identify multiple boot images within an ISO and allows you to select which one to extract, or extract all of them.

The extracted image is typically a raw disk image (e.g., a floppy disk image, a hard disk image, or a non-emulated boot sector) that can then be written directly to a device (like a USB stick) using tools such as dd. It is commonly found as part of packages that deal with bootloaders or ISO image manipulation, serving as a crucial step in the process of transferring bootable content from optical media to other storage devices.

Requires the input ISO image to be compliant with the El Torito bootable CD-ROM specification.
May not correctly identify or extract boot images from non-standard or proprietary ISO formats.
The extracted image is a raw binary image and must be written to a suitable device (e.g., USB drive) using tools like dd to become bootable. It does not modify the original ISO file.

Extracting the first boot image to a file named 'boot.img':
geteltorito -o boot.img my_iso.iso

Writing the extracted image to a USB stick (replace /dev/sdX with your actual device):
sudo dd if=boot.img of=/dev/sdX bs=4M status=progress
(Always double-check the target device path, as incorrect usage of dd can lead to data loss.)

Listing available boot images and their details (often prints to stderr):
geteltorito my_iso.iso
Alternatively, for more detailed information about boot images within an ISO:
isoinfo -d -i my_iso.iso

geteltorito is often distributed as part of the syslinux project or other bootloader utility suites. Its purpose is to facilitate the use of El Torito boot images, which became standard for making CDs bootable in the mid-1990s. Its development closely tracks the need for extracting and deploying these bootable images, especially for creating bootable USB drives as optical drives became less common, making it a vital component in modern bootable media creation workflows.

dd(1), isoinfo(8), xorriso(1), mkisofs(8), genisoimage(8)