I would have a different approach at this point. What about writing the
original .ISO image to the USB key ( as opposed to keeping in a directory
on a USB key and use Ventoy ), then just copy the autoinst file on the root
directory of the USB key ? I would be curious to try this.
On Fri, Aug 22, 2025 at 4:02 PM Robert P. J. Day via linux <
linux [ at ] linux-ottawa [ dot ] org> wrote:
>
> i will recap the fight i am currently having in trying to create a
> bootable USB drive from Ubuntu Server 24.04.3 ["24.04"], and i will
> interac $100 to the first person who can solve the problem i am about
> to describe. (i will start writing this up in detail at my
> crashcourse.ca wiki, but i'll supply enough here that you will have
> enough information to take a crack at it.)
>
> previously, i described how i want to customize a 24.04 ISO image to
> add some autoinstall configuration, but the problem here is way
> simpler -- i just want to take that original ISO and turn it into a
> bootable USB drive *as is*. but wait ... there's more.
>
> if i just want an equivalent bootable USB drive from the ISO image,
> well, that's trivial -- just "dd" from the ISO image to the USB drive.
> that works just fine and, when i do that, the USB drive is recognized
> by two different appliances i'm playing with when i go into the BIOS
> on either appliance, go top the "Boot" menu, and i can see that both
> BIOSes list the USB drive as a boot option. in short, those USB drives
> are visible as bootable devices. and that's what i'm after.
>
> but i don't just want to use "dd" -- that's too easy. rather, i want
> to take the 24.04 ISO image and *unpack* it ("mount -o loop",
> "bsdtar", whatever) to get the directory structure, which is where i
> would add the autoinstall stuff, but i want to keep it simple, and
> after i unpack the ISO image, i'm happy to *immediately* pack it up
> again (unchanged) to get the equivalent bootable ISO image. then i can
> "dd" that to a USB drive and boot from that.
>
> that's it -- i want to take canonical's 24.04 ISO image, unpack it
> (however you want), then recreate a bootable ISO image from that (most
> likely with "xorriso"), dd to USB drive and boot from that. and from
> my poking around, it seems like the work involves invoking "xorriso"
> with all of the appropriate options, a good example seen here:
>
>
> https://www.reddit.com/r/Ubuntu/comments/1g0cq09/how_to_create_a_custom_ubuntu_24041_image_by/
>
> that makefile ostensibly does what i want, except we can ignore all
> the cloud-init stuff since i don't want to make any changes, and the
> real work is done by the "ubuntu" target, which runs "xorriso" with a
> truckload of options in order to recreate a bootable ISO image.
>
> i used something very much like that but, no matter how i tweak it,
> once i recreate an ISO image and copy to USB drive, neither appliance
> recognizes that USB drive as a boot option, so i am clearly
> overlooking something critical.
>
> there's the $100 bounty -- figure out the magic incantation of
> "xorriso" that allows me to do the above:
>
> 1) start with canonical 24.04.3 ubuntu server image
> 2) unpack into directory structure
> 3) use xorriso to immediately repack into bootable ISO image
> 4) copy to USB drive, and boot from that USB drive
>
> i've played with those options all morning and haven't succeeded.
> thoughts?
>
> rday
>
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