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

[Roderick Smith]

I recommend that the ESP's size exceed 200 MiB. The reason is that some
boot loaders, such as ELILO, effectively require kernels to reside on
the ESP. There's also a patch to effectively make the Linux kernel its
own EFI boot loader, which would also require the kernel to reside on
the ESP. If kernels go on the ESP, then the ESP's size requirements
become similar to those for a separate /boot partition. An Ubuntu kernel
and initial RAM disk together consume about 20 MiB, and I've seen them
much bigger than this, so even a 100 MiB might not hold many kernels.
(Fedora creates 500 MiB /boot partitions, as a point of comparison.)

I realize that Ubuntu uses GRUB 2 and so does not need to place kernels
on the ESP; however, individual users might decide to ditch GRUB 2 in
favor of ELILO or even the experimental kernel patches, and users might
dual-boot with a distribution that does use ELILO, such as OpenSUSE.
Note that Ubuntu includes an ELILO package in its repositories, so it's
a logical boot loader for an Ubuntu user to try if GRUB 2 gives
problems.

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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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