I tried to unpack an ISO of Ubuntu to USB stick without writing it (i can't use superuser utilities like dd or Rufus). Then i set my USB stick first in UEFI boot priority. I got working GRUB, but when i tried to run the system in live i got this error:

Initramfs unpacking failed: Decoding failed;
Unable to find a medium container a live file system
Attempt interactive netboot from a URL?

Maybe there is a way to run it from grub shell?

  • To create a bootable USB, you need to create a boot partition, which is what Rufus, UNetbootin and other utilities do. See alternativeto.net/software/unetbootin for alternatives, but you'll need to run as sudo to install. If you have access to a Windows machine, you can create a USB there with Rufus. Oct 25 '20 at 17:58
  • @DrMoishePippik but it seems to run .efi files fine even without boot partition on USB stick.
    – DenisNovac
    Oct 26 '20 at 4:15

After some tries i found out i can repack Arch (it was archlinux-2020.10.01-x86_64 image) and some UEFIs will be able to run it's grub. The Arch itself won't run but it will startup an emergency shell (which seems to not be a thing in Ubuntu). This shell have mount and dd utilities, so it is possible to create a bootable device afterwards. And you don't need superuser rights to just repack an ISO to USB stick (in fact, it was done with SD-card on non-root Android smartphone). It worked on 2 out of 3 laptops i tried.

So i repacked an arch.iso into SD-card and also placed ubuntu.iso into it. In Arch's emergency shell i wrote ubuntu.iso into the USB stick by dd. And then i was finally able to run it.

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