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

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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.

** Affects: syslinux (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: bot-comment
-- 
Unable to boot LiveCD ISO from UDF filesystem
https://bugs.launchpad.net/bugs/1820222
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