[Bug 1851311] Re: loopback command hangs in 2.04 under UEFI

[PJSingh5000]

I did additional testing, and I can confirm that adding "rmmod tpm" does
indeed work...

See comment number 51 by Alkis
(https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/1851311/comments/51).

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    menuentry "Install" {
        set isofile="/ubuntu.iso"
        rmmod tpm
        loopback loop (hd0,2)$isofile
        linux (loop)/casper/vmlinuz boot=casper iso-scan/filename=$isofile noprompt noeject
        initrd (loop)/casper/initrd
    }
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The Busy Box error I had experienced was actually due to a bad ISO file.

I tested "rmmod tpm" on a system running Ubuntu 19.10.

I tested two official Ubuntu *.iso files:
- Ubuntu 18.04
- Ubuntu 20.04

In both cases, the system successfully booted the specified *.iso.

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https://bugs.launchpad.net/bugs/1851311

Title:
  loopback command hangs in 2.04 under UEFI

Status in grub2 package in Ubuntu:
  Confirmed
Status in grub2 package in Debian:
  Unknown

Bug description:
  Trying to loop mount ISO.

  Installed grub 2.04 to flash drive in UEFI mode from 19.10
  Flash drive does not boot and gives Out of memory error & no server error. Must load kernel first.

  Re-installed grub from 18.04 to same flash drive using same boot stanza.
  Booted without issue.

  From 18.04
  fred at Bionic-Z170N:~$ grub-install -V
  grub-install (GRUB) 2.02-2ubuntu8.13

  from 19.10
  fred at fred-Z170N-eoan:~$ grub-install -V
  grub-install (GRUB) 2.04-1ubuntu12

  Boot stanza that works in 2.02 but not in 2.04

  menuentry "Focal Live ISO" {
  set isofile="/ISO/focal-desktop-amd64.iso"
  loopback loop (hd0,1)$isofile
      linux (loop)/casper/vmlinuz boot=casper iso-scan/filename=$isofile toram noeject
      initrd (loop)/casper/initrd
  }

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