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Thread: Creating custom ISO

  1. #1
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    Jan 2021
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    Creating custom ISO

    I am trying to create a custom ISO which I want to modify for unattended installation.

    I am able to create the ISO but it seems I cannot make it bootable.
    When I use the same procedure for a Window 10 ISO it works just fine. On Windows 10 I am using efisys.bin as bootfile.
    And don't hate me - I am creating the custom ISO on a Windows machine using Powershell

    I have tried using efi.img and that makes it bootable - but into a Grub command line and not starting the normal installer.

    I am using this iso file as my base ubuntu-20.04-live-server-amd64.iso (which I have extracted the content and then recreated as my customimage.iso)

    My guess is I just need the correct boot file to make it work but I can can't find it anywhere.

  2. #2
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    Jun 2014
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    Re: Creating custom ISO

    I am creating the custom ISO on a Windows machine using Powershell
    I think you will have to post a lot more detail if you want help. Specific steps you took to do this, explain what the 'procedure' is. Do you want to boot the usb in UEFI mode, Legacy/CSM mode or both? Live Linux install systems can use Grub or Syslinux/Isolinux. Which are you using?

  3. #3
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    Jan 2021
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    Re: Creating custom ISO

    At first I "just" want to rebuild ubuntu-20.04-live-server-amd64.iso.
    The official iso boots just fine in my virtual machine - and I want my custom iso to do the same.

    I am booting it as UEFI.

    My procedure is
    1) Mouting
    ubuntu-20.04-live-server-amd64.iso
    2) Copy content of mounted drive to a folder
    3) Writing the content to a new iso
    4) Writing the bootloader with a boot file with
    efi.img

    But it seems that efi.img is the wrong file since it only boots into a command line instead of the regular installer as when you boot ​ubuntu-20.04-live-server-amd64.iso


  4. #4
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    Re: Creating custom ISO

    What commands did you use for steps 3 and 4. If you are doing this in a directory (folder) you would then need to create an iso (or img file) of it. Creating an iso would generally include installing a bootloader and the common tools for this are mkisofs, genisoimage and xorriso. Some discussion of the last 2 at the Debian site below. I've always used iso so don't know about img files or what differences there might be. If you had a usb mounted to the folder on your drive, you could use the first 2 steps but would still have to install a bootloader.i

    https://wiki.debian.org/genisoimage


  5. #5
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    Jan 2021
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    14

    Re: Creating custom ISO

    It is a iso file I am trying to create.

    But have done some more testing and I am a bit closer now.

    For some reason my custom iso does not load grub.cfg (which show the install options) when it boots.
    So it just show the GRUB command line.

  6. #6
    Join Date
    Jun 2014
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    6,083

    Re: Creating custom ISO

    So it just show the GRUB command line.
    To state the obvious, Grub wasn't installed properly and no one can tell you what or if you did something wrong as we don't know what you did?

  7. #7
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    Jan 2021
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    Re: Creating custom ISO

    I am not sure how to make it clearer.

    I need the bootloader file that was used to create the original ubuntu-20.04-live-server-amd64.iso.On windows it's included on the dvd. Pretty easy. On Ubuntu not so much.

  8. #8
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    Re: Creating custom ISO

    When I use the same procedure for a Window 10 ISO it works just fine. On Windows 10 I am using efisys.bin as bootfile.
    The procedure you use for windows is unlikely to work on Linux. Doubt that efisys.bin will work. Are you following instructions from a specific web site? If so, post a link. I'm not sure you can do this from windows powershell. I did an online search and everything I found using powershell was to create a bootable windows.

    Writing the content to a new iso
    Writing the bootloader with a boot file with
    efi.img
    Listing the specific commands you used in the two steps above might help someone to help you. Also, what did you use to install Grub and also how did you create the iso, what commads. I've not tried this with windows powershell so doubt I'll be able to help.

  9. #9
    Join Date
    Jan 2021
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    14

    Re: Creating custom ISO

    I am using this powershell script to create the ISO

    https://gallery.technet.microsoft.co...ction-a8deeffd

    The script basically takes two inputs a source folder and a bootloader file.
    When I use the efi.img bootloeader file from the Ubuntu ISO it does not work as expected.

  10. #10
    Join Date
    Jun 2014
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    6,083

    Re: Creating custom ISO

    After reviewing the page and the script on it which you posted, I don't see any indication that one would expect to be able to use it for anything other than selected windows versions which are listed at the bottom of the page. Your unsuccessful efforts would seem to confirm that. If you are using an Ubuntu install to make your customized iso there are ways to do that. Do you actually have Ubuntu installed to a hard drive or are you using the iso (extracted and coped)? If you are just looking for a challenge by using windows powershell, I don't have any ideas or know of any software that would do this. Good luck.

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