ok, will test this later this evening or tomorrow morning, but as i mentioned, i followed the instructions at that link fairly closely and, while the xorriso command ultimately created an ISO image, it was not recognized as a bootable device. so somewhere along the line, i missed something. more later. rday On Fri, 22 Aug 2025, Qingwei Zhang via linux wrote: > HI Robert, > > Thank you for the follow-up. That's a great question. > > The solution you found on Reddit is excellent and will work. Both methods achieve the same goal: > creating a proper hybrid-bootable ISO. The difference is only in the approach. > > The Reddit method uses a single, complex command to copy the required boot data directly from the > original ISO during the build process. > > My method is more explicit: it first extracts that same boot data into separate files, and then uses > those files to build the new ISO. > > The "extra steps" are just a different way of providing xorriso with the same essential information. > Either method will produce the bootable USB drive you need. > > Best regards, > Qingwei > > On Fri, Aug 22, 2025 at 5:29 PM Robert P. J. Day via linux <linux [ at ] linux-ottawa [ dot ] org> wrote: > > i'm about to start testing this possibility, but i'm still curious > as to why it seems to need a couple extra steps compared to this > alleged solution: > > https://www.reddit.com/r/Ubuntu/comments/1g0cq09/how_to_create_a_custom_ubuntu_24041_image_by/ > > do the steps at that link simply not work? > > On Fri, 22 Aug 2025, Qingwei Zhang via linux wrote: > > > > HEY ROBERT, > > > > SAW YOUR EMAIL ABOUT THE UBUNTU ISO. > > > > PLEASE TRY THIS WAY, I THINK IT WILL WORK: [LINK TO THE SOLUTION STEPS] > > > > LET ME KNOW. > > > > BEST, > > > > QINGWEI > > > > > > STEP 1: SET UP YOUR WORKSPACE > > > > First, create a workspace, unpack the ISO’s file content, and extract the specific > boot files needed > > by xorriso. > > > > # 1. Create directories for your work > > mkdir -p ubuntu-custom/iso_contents > > mkdir -p ubuntu-custom/boot_files > > > > # 2. Define the original ISO path > > ORIGINAL_ISO="ubuntu-24.04.3-live-server-amd64.iso" > > > > # 3. Unpack the ISO contents using bsdtar (it handles rock ridge, etc. well) > > # Using 'mount -o loop' is not sufficient as it doesn't expose the boot images. > > bsdtar -C ubuntu-custom/iso_contents -xf "$ORIGINAL_ISO" > > > > # 4. Extract the MBR boot code template from the original ISO > > dd if="$ORIGINAL_ISO" bs=1 count=432 of=ubuntu-custom/boot_files/isohdpfx.bin > > > >___________________________________________________________________________________________________ > _ > > > > STEP 2: THE XORRISO COMMAND TO REBUILD THE ISO > > > > This is the critical step. The following command tells xorriso to rebuild the ISO > while embedding > > all the necessary boot information for BIOS and UEFI systems. Run this from the > ubuntu-custom > > directory. > > > > # Change into the working directory > > cd ubuntu-custom/ > > > > # The magic incantation > > xorriso -as mkisofs \ > > -r \ > > -V "Ubuntu 24.04.3 LTS" \ > > --grub2-mbr boot_files/isohdpfx.bin \ > > --protective-msdos-label \ > > -partition_offset 16 \ > > --mbr-force-bootable \ > > -append_partition 2 0xef iso_contents/boot/grub/efi.img \ > > -appended_part_as_gpt \ > > -iso_mbr_part_type 0x00 \ > > -c boot/boot.cat \ > > -b boot/grub/i386-pc/eltorito.img \ > > -no-emul-boot -boot-load-size 4 -boot-info-table --grub2-boot-info \ > > -eltorito-alt-boot \ > > -e boot/grub/efi.img \ > > -no-emul-boot \ > > -o ../rebuilt-ubuntu-server.iso \ > > iso_contents/ > > > >___________________________________________________________________________________________________ > _ > > > > STEP 3: CREATE THE BOOTABLE USB > > > > Once the rebuilt-ubuntu-server.iso is created, write it to your USB drive using dd. > > > > 1. Identify your USB drive with lsblk. Be absolutely certain of the device name > (e.g., /dev/sdc). > > Using the wrong device will destroy data. > > 2. Write the ISO to the drive. > > > > # Replace /dev/sdX with your actual USB device name > > sudo dd if=../rebuilt-ubuntu-server.iso of=/dev/sdX bs=4M status=progress oflag=sync > > > > The oflag=sync flag ensures all data is physically written before the command returns. > The resulting > > USB drive should now be recognized as bootable by your appliances. > > > >___________________________________________________________________________________________________ > _ > > > > On Fri, Aug 22, 2025 at 4:45 PM Dnkorovkin via linux <linux [ at ] linux-ottawa [ dot ] org> wrote: > > Hi Robert. > > I am quite busy at the moment to try it, but the general idea of it is: > > 1. mount the disk image with mount -o loop > > 2. cp -a source to usb > > 3. Run syslinux to make bootable USB drive. > > > > Hope this helps, > > > > Dmitriy > > > > -------- Original message -------- > > From: "Robert P. J. Day via linux" <linux [ at ] linux-ottawa [ dot ] org> > > Date: 2025-08-22 16:00 (GMT-05:00) > > To: OCLUG mailing list <linux [ at ] linux-ottawa [ dot ] org> > > Subject: [linux] $100 bounty for resolving my issue for creating bootable USB drive > > > > > > 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 > > > > To unsubscribe send a blank message to linux+unsubscribe [ at ] linux-ottawa [ dot ] org > > To get help send a blank message to linux+help [ at ] linux-ottawa [ dot ] org > > To visit the archives: https://lists.linux-ottawa.org > > > > > > > > >