I really need to be able to do at least one of two things:

  • Convert an ISO file which is in the ISO9660 format to an ISO that uses the EXT4 format.

  • Transform a bootable drive which is in EXT4 into an ISO of the EXT4 file system.

It can't be ISO9660 because correct me if I'm wrong, but as I understand it, ISO9660 is only for CDs/DVDs, but I want to use a USB stick. I created these files using Linux Live Kit (it gives me an ISO9660 file and a ZIP file which can be made into a bootable drive, which I used on an EXT4 drive). I can boot the drive (though only in Legacy/CSM mode for some reason, but I'd prefer UEFI - can I do that?), but what I really need to do is boot this using Ventoy, which requires an ISO, and it seems that ISO9660 gives it an error such that it can't recognize the file system. Hence the reason why I'm trying to make an ISO with EXT4 from the data on the EXT4 bootable drive.

I've tried doing so using dd and Disks, but it makes a 4.3 GB file and then says there's not enough space, even though the drive that I'm saving it onto will hold many additional GB, so I think (but I'm not certain) that it's complaining that it can't be more than 4.3 GB because that's the max size of a DVD (but I don't see why it turns out that big, anyway, because even though the installation is more than 7 GB, the ISO9660 and the ZIP file are both like 1.5 GB).

So, what am I doing wrong?

  • You can't boot from an ISO. It's a disk image & must be mounted. At boot, there is nothing to mount it. What you need to do is ask us about what you are actually trying to achieve, rather than about how you think you could achieve it.
    – Tetsujin
    Nov 28, 2020 at 19:06
  • Actually, Ventoy absolutely CAN boot from an ISO! Multiple different ones even. You install Ventoy onto a USB stick and it automatically puts it on the second partition, and then you copy ISO files onto the first partition. Then when you boot Ventoy it lets you choose from a list of ISO files. It all works up to that point, but when I try to boot my custom ISO it crashes with an error that it doesn't recognize the file system, and since it's ISO9660 rather than EXT4, and trying to run on USB, I thought that might be why.
    – ThisIsMe
    Nov 28, 2020 at 19:11
  • 1
    And to answer your question, what I'm trying to achieve is to be able to customize an ISO file for several different distributions of Linux, and have them all multiboot, each into live mode (ideally loaded into RAM), but WITHOUT persistence, because I want to keep all of my customizations/installations, but not allow any new changes after that, and to save on wear and tear by essentially making the drive read-only.
    – ThisIsMe
    Nov 28, 2020 at 19:13
  • So perhaps that's what your question ought to focus on.
    – Tetsujin
    Nov 28, 2020 at 19:15
  • Sure, but I've already looked into it and tried every conceivable alternative, and narrowed it down to the only thing that seems like it MIGHT possibly work. And the problem with asking questions about what to do rather than how to do it is that people answer me by saying to do things that I've already been trying and failing to do, but they don't say how, so I thought that I'd skip right to the how part. In any case, if you have a better alternative I'm open to it (though I've probably tried it), but do you know actually how to do what I'm trying to accomplish?
    – ThisIsMe
    Nov 28, 2020 at 19:35


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