[Bug 702283] Re: usb-creator doesn't create EFI-bootable USB sticks

[Evan Broder]

If I understood mjg59's posts on EFI correctly, you don't actually need
the hybrid monstrosity to support EFI. Several of the more insidious
features of the mjg59's hybrid were only needed to support the scenario
where you directly dd an ISO onto a USB drive.

In fact, based on some quick experimentation with my UEFI-enabled laptop
(a ThinkPad T420), the Ubuntu ISOs we're generating now support 64-bit
UEFI firmwares, even after being run through usb-creator. Specifically:

 - The build process generates a FAT32 filesystem image at
boot/grub/efi.img which contains a efi/boot/bootx64.efi file, and points
a secondary El Torito record at that image with PlatformId 0xEF. This
enables UEFI-bootable CDs

 - The build process also generates a efi/boot/bootx64.efi, which usb-
creator will copy onto the FAT32 filesystem it creates on USB drives,
which is sufficient to make a removable USB drive UEFI-bootable

Remaining issues:

 - The FAT32 partition created by usb-creator won't have a partition
type of 0xEF, so some firmwares may not identify it as a UEFI system
partition and may not look for the bootloader there. My UEFI laptop
doesn't have this problem, but I have a sample size of 1 to work off of.

 - Some (64-bit) Apple machines have a 32-bit EFI firmware. Since the
Ubuntu CDs don't include an efi/boot/bootia32.efi (either directly or in
the El Torito image), these machines won't recognize them. It would be
easy to add the 32-bit image, but we'd need to find an extra megabyte of
space or so, since the image contains 2 copies of the firmware.

 - Some *really* old Macs don't use El Torito for CDs at all, and
instead look for an Apple partition map. This is the point you have to
start pulling in some of mjg59's monstrosity to create CD images that
boot on those machines. Personally, I'm not convinced the effort to
reward payout is there, since we're talking about fairly old machines at
this point, but I tend to be more conservative on that sort of thing.

The original report also mentioned the CR-48. These, too, are a special
case, because they will only ever boot off of external media signed by
Google, so nothing we can do will make USB sticks that will boot on
those.

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https://bugs.launchpad.net/bugs/702283

Title:
  usb-creator doesn't create EFI-bootable USB sticks

Status in “usb-creator” package in Ubuntu:
  Triaged

Bug description:
  Binary package hint: usb-creator

  USB startup disk creator seems to create USB disks which can boot on
  traditional BIOS based PC's but not EFI based computers such as Apple
  Mac laptops, Jogglers, Google CR-48. This reduces the number of people
  who can test Ubuntu on machines that could significantly benefit from
  the testing.

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