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

[Paul White]

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

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https://bugs.launchpad.net/bugs/1820222

Title:
  Unable to boot LiveCD ISO from UDF filesystem

Status in syslinux 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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