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

[PJSingh5000]

@Alkis Georgopoulos,

Thanks for the suggestion.
I added "rmmod tpm".
Unfortunately, it did not really help my situation...

$ sudo update-grub
    - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    Sourcing file `/etc/default/grub'
    Sourcing file `/etc/default/grub.d/init-select.cfg'
    Generating grub configuration file ...
    Found linux image: /boot/vmlinuz-5.3.0-51-generic
    Found initrd image: /boot/initrd.img-5.3.0-51-generic
    Found linux image: /boot/vmlinuz-5.3.0-46-generic
    Found initrd image: /boot/initrd.img-5.3.0-46-generic
    Adding boot menu entry for EFI firmware configuration
    done
    - - - - - - - - - - - - - - - - - - - - - - - - - - - -

$ sudo nano /etc/grub.d/40_custom
$ sudo update-grub
    - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    Sourcing file `/etc/default/grub'
    Sourcing file `/etc/default/grub.d/init-select.cfg'
    Generating grub configuration file ...
    Found linux image: /boot/vmlinuz-5.3.0-51-generic
    Found initrd image: /boot/initrd.img-5.3.0-51-generic
    Found linux image: /boot/vmlinuz-5.3.0-46-generic
    Found initrd image: /boot/initrd.img-5.3.0-46-generic
    Adding boot menu entry for EFI firmware configuration
    done
    - - - - - - - - - - - - - - - - - - - - - - - - - - - -

$ cat /etc/grub.d/40_custom
    - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    #!/bin/sh
    exec tail -n +3 $0
    # This file provides an easy way to add custom menu entries.  Simply type the
    # menu entries you want to add after this comment.  Be careful not to change
    # the 'exec tail' line above.

    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
    }
    - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Prior to this change, I would get a blank screen with a whirring fan.

With the above change, I do see the boot-up log messages.
But, I get a busy box...
    - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    BusyBox v1.301 (Ubuntu 1:1.30.1-4ubuntu4) built-in shell (ash)
    Enter 'help' for a list of built-in commands.

    (initramfs) Begin:  Running /scripts/casper-premount ... done.
    Begin: waiting for devs... ... done.
    touch /dev/.initramfs/lupin-waited-for-devs: No such file or directory
    stdin: Invalid argument
    done.
    loop: can't get info on device /dev/loop1: No such device or address
    - - - - - - - - - - - - - - - - - - - - - - - - - - - -

I don't know why it is referencing "loop1" ?

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Foundations Bugs, which is subscribed to grub2 in Ubuntu.
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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