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

[Adam Thompson]

Ah, I see what you mean.
HP appears to be breaking that paradigm, however, in that they have UEFI firmware that supports "legacy mode" booting, and that they seem to be shipping systems with normal MBR-style partition tables that nonetheless have EFI boot partitions.
My understanding of how Windows boots is, I think, the same as yours - although its legacy boot mode is very similar to EFI boot now, it's still different.  So WTF is/are HP and Lenovo and Acer [I think], and... etc. doing?
The existence of this hybrid non-GPT-but-still-EFI firmware and accompanying boot process, unless I'm missing some important detail, will require that Ubuntu and others abandon their very limited notions of UEFI-compliance and allow much greater flexibility.
Meanwhile, I'm thankful that the Ubuntu systems I manage still have the ability to boot in 'normal' legacy mode.  (As does the HP 8200 - if you're willing to wipe the existing disk, everything works just fine.)

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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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