[Bug 1820222] Re: Unable to boot LiveCD ISO from UDF filesystem

[Steve Langasek]

This is presumably because you are on a system using UEFI with
SecureBoot, and therefore the loading of external grub modules fails
('insmod udf'), and we do not build udf support into the signed UEFI
GRUB image.

Because the UEFI GRUB image is signed into the SecureBoot regime as
trusted code, the standards for security are higher, and we would no
simply enable an additional filesystem driver without some measure of
security review.

** Package changed: syslinux (Ubuntu) => grub2 (Ubuntu)

** Changed in: grub2 (Ubuntu)
   Importance: Undecided => Wishlist

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Title:
  Unable to boot LiveCD ISO from UDF filesystem

Status in grub2 package in Ubuntu:
  New

Bug description:
  Using Lubuntu 18.04.2 (#lsb_release -a -> Description:  Ubuntu 18.04.2
  LTS)

  In order to resolve a problem with booting after 'Software Updater'
  updated the system, I needed to boot from a LiveCD and chroot to
  resolve the boot issue.

  GRUB allows systems to boot from an ISO image located on an accessible
  filesystem, so if you have sufficient disk space, you do not need to
  write out to a USB flash drive.

  I downloaded the Lubuntu 18.0.2 from
  http://cdimage.ubuntu.com/lubuntu/releases/18.04.2/release/ onto a
  spare partition formatted as UDF version 2.0.1 and confirmed the
  integrity of the download with sha256sum

  On attempting to boot from the ISO directly using GRUB, the boot
  fails. As I don't have a serial console I can't give the exact error.

  As I knew I could boot from other ISO images on a separate ext2
  partition, I copied the Lubuntu 18.04.2 ISO to the ext2 partition.
  Attempting to boot with the ISO in this location worked, I got a
  LiveCD system from which I could then do the necessary chroot
  operations to get my system working again.

  GRUB script - fails when ISO is on UDF formatted partition, succeeds
  when on ext2 partition

  setparams 'Lubuntu 18.04.2 ISO'
  insmod iso9660
  insmod ext2
  insmod udf
  insmod part_gpt
  set isofile="/lubuntu-18.04.2-desktop-amd64.iso"
  loopback loop (hd1,gpt5)$isofile
  linux (loop)/casper/vmlinuz boot=casper iso-scan/filename=$isofile noprompt noeject toram --
  initrd (loop)/casper/initrd

  I suspect the iso has been produced without including udf filesystem
  drivers somewhere. I suggest supporting UDF would be helpful as many
  people use UDF as a cross-platform alternative to FAT as it supports
  larger file sizes than FAT.

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