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I trying to understand it right. isohybrid is a tool to make Ubuntu iso bootable - see mkusb.

Cloning an iso file to a mass storage device makes a boot drive, provided it is a hybrid iso file, post-processed with isohybrid. See this link to the isohybrid sub-page.

Also on same link:

mkusb will 'use the whole device', actually only the head end (size of the iso file), but the rest of the device is not available. mkusb simply clones the ISO 9660 file system with its content from the iso file. This ISO 9660 file system works from CD/DVD disks, and also from USB drives. After using a USB pendrive like this, you make a new partition table and file system, if you want to use it for another purpose.

But in wikipedia Hybrid_disc:

A hybrid disc is an optical disc that has multiple file systems installed on it, typically ISO 9660 and HFS+ (or HFS on older discs). One reason for the hybrid format is the restrictions of ISO 9660 (filenames of only eight characters, and a maximum depths of eight directories, similar to the Microsoft FAT file system).

So do I understand it correctly that isohybrid tool makes ordinary ISO 9660 images, not hybrid ones? What is the meaning of hybrid apex in isohybrid, why is it not called something like isoboot? I could not find that "historic" info via web search.

Marisha
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1 Answers1

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Hybrid iso file and program isohybrid

The program isohybrid from the package syslinux-utils converts

  • an iso file that can be burned to a bootable CD/DVD

to

  • a hybrid iso file, that can be

    • burned to a bootable CD/DVD and
    • cloned to a bootable mass storage device: USB pendrive, USB SSD, memory card, internal HDD, internal SSD ...

It is possible to use the robust cloning method to create a boot drive from a mass storage device (most often a USB pendrive).

isohybrid adds some code near the head end of the iso image in order to make this possible.

Please notice that isohybrid should be used only once. Do not you use it on an iso file, that has already this hybrid feature. Most (but not all) linux distros are distributed as hybrid iso files.

I don't know the history of the word isohybrid, but I have used this tool myself, when I made bootable iso files 'from scratch', and I have used it to convert CD/DVD-only iso files for years. Nowadays I seldom use it, because most iso files that I download are already 'isohybrid' iso files, that boot also when cloned into a USB pendrive.

Links

wiki.syslinux.org/wiki/index.php?title=Isohybrid

wiki.osdev.org/El-Torito

A hybrid disc is something else

The link in your question about 'hybrid disc' is describing something else, not a hybrid iso file. The similar names can cause confusion.

sudodus
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  • @C.S.Cameron, You are welcome :-) – sudodus Oct 20 '19 at 15:28
  • Hi! isohybrid: image.iso: could not find boot record after mkisofs -lJR -o image.iso directory_name directory_name is loopmounted hybrid iso that resulted in properly booting USB. What is wrong? If too complex for comment, than I see a new question is needed. – Martian2020 Nov 28 '21 at 04:46
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    @Martian2020, It is often best to create an own question, where you can describe what you have, what you have done, what you want and what went wrong. Please put a link to the new question here. – sudodus Nov 28 '21 at 04:52
  • https://askubuntu.com/questions/1378005/isohybrid-image-iso-could-not-find-boot-record – Martian2020 Nov 28 '21 at 05:13