[Bug 2038694] Re: Now that exfat filesystem is in the kernel, allow using it for storing isos loopback booting and storing the persistence file

[Adam Vodopjan]

Previously I created a script to make ubuntu iso images bootable from
f2fs partitions. After discovering this bug, I converted it into a
generic "make casper aware of fs X, add kernel modules Y to the initrd"
one.

You can get it here https://github.com/slowpeek/ubuntu-remaster-bbb and
make 20.04+ images bootable from exfat like this:

  ubuntu-remaster-exfat input.iso output.iso

or, without the exfat shortcut:

  ubuntu-remaster-bbb --fs exfat --module exfat input.iso output.iso

If using the docker image:

  ubuntu-remaster-bbb.docker --fs exfat --module exfat -- input.iso
output.iso


This way 18.04.5+ can boot from exfat as well, but only with the hwe kernel. Hence in case of live-server 18.04.5+, extra '--hwe-only' option is required.

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https://bugs.launchpad.net/bugs/2038694

Title:
  Now that exfat filesystem is in the kernel, allow using it for storing
  isos loopback booting and storing the persistence file

Status in casper package in Ubuntu:
  Confirmed

Bug description:
  Recent Ubuntu Desktop livecd isos are greater than 4G and have been
  growing at an alarming rate (22.04.1 is 3.6G and 22.04.2 is 4.6G, but
  that's another story). The fat32 filesystem allows a maximum of 4G
  file size, so newer isos can not be stored on fat32. Currently the
  only non-journalled filesystem and only file system with easy
  interoperability with Windows is fat32. Neither NTFS nor EXFAT are
  supported by casper. EXFAT would be good to support so that a windows
  user can write a greater than 4G iso file from Windows to use for
  loopback booting. And likewise allow the persistence file to be on
  EXFAT, so that another filesystem is not needed just to store the
  persistence file.

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