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

[C.S.Cameron]

@alkisg Thank you for the workaround, easier that installing grub 2.02
via mkusb.

I put `rmmod tpm` on it's own line in grub.cfg, above the "loopback loop
$isofile" line.

Booting BIOS mode grub 2.02 I get "error: no such module" and then after
a bit it boots okay.

Booting UEFI mode grub 2.04 it boots with no error messages.

Both modes go to Disk Check.

Neither mode goes to the Try/Install screen when booting, nor to remove
drive and press enter when quitting.

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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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