[Bug 811485] Re: EFI SYSTEM PARTITION should be atleast 100 MiB size and formatted as FAT32, not FAT16

[cfr]

I'm far from confident about this but running Ubuntu's installer on my
machine finally allowed me to boot from a GPT partitioned disk. Not
immediately because the installer crashed and although it wiped my EFI
system partition, it didn't get around to putting anything else in it
afterwards. And even when I copied my backup back, the UUIDs didn't
match thus causing trouble for my intact install of linux. But at least
I could get to a grub prompt after copying my backed up ESP back. That
was a huge improvement. And after fixing the UUID, I have a working
installation of linux. (Not of Ubuntu, obviously.)

As far as I can tell, the only thing Ubuntu's installer did which I
didn't do was to use fat16 rather than fat32 to format the partition. I
am almost certain that my machine would have remained unbootable if it
had used fat32.

I found a reference in bug #769669 to a minimum size for the fat32
partition of 256M. That might explain why my machine was not booting. My
EFI partition is only 202M. But if that is why, the installer should
also insist on a partition which meets that requirement if it switches
to fat32 for the EFI partition.

My machine has Phoenix SecureCore Tiano firmware. Version 1.14.

Reference: https://bbs.archlinux.org/viewtopic.php?pid=1024473#p1024473

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https://bugs.launchpad.net/bugs/811485

Title:
  EFI SYSTEM PARTITION should be atleast 100 MiB size and formatted as
  FAT32, not FAT16

Status in “partman-efi” package in Ubuntu:
  Confirmed

Bug description:
  Create a EFI SYSTEM PARTITION of minimum 100 MiB size (200 MiB
  recomended). Also partman-efi should use FAT32 instead of FAT16 for
  EFI SYSTEM PARTITION as mandated by the UEFI 2.3.1 Spec. FAT16 ESP
  partition is not recognised by Windows 7 UEFI bootloader because of
  this.

  The below quote is copied form the UEFI Specification 2.3.1 - Chapter
  12.3 File System Format.

  [QUOTE]
  EFI encompasses the use of FAT32 for a system partition, and FAT12 or FAT16 for removable media. The FAT32 system partition is identified by an OSType value other than that used to identify previous versions of FAT. This unique partition type distinguishes an EFI defined file system from a normal FAT file system. The file system supported by EFI includes support for long file names.

  FAT defines that all files in a directory must have a unique name, and
  unique is defined as a case insensitive match.

  UEFI does not impose a restriction on the number or location of System Partitions that can exist on a system. System Partitions are discovered when required by UEFI firmware by examining the partition GUID and verifying that the contents of the partition conform to the FAT file system as defined in Section 12.3.1.1. Further, UEFI implementations may allow the use of conforming FAT partitions which do not use the ESP GUID. Partition creators may prevent UEFI firmware from examining and using a specific partition by setting bit 1 of the Partition Attributes (see 5.3.3) which will exclude the partition as a potential ESP.
  [/QUOTE]

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