UEFI: No option to format EFI system partition

[Russell Phillips]

Installing Ubuntu 16.10-amd64-desktop on a UEFI system.

Using fdisk, I build a new GPT with the first partition being a 128MB EFI System Partition:

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Disk /dev/sda: 465.8 GiB, 500107862016 bytes, 976773168 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: 85CA3211-D280-41FB-81C3-D81053A34B82

Device Start End Sectors Size Type
/dev/sda1 2048 264191 262144 128M EFI System
/dev/sda2 264192 67373055 67108864 32G Linux root (x86-64)
/dev/sda3 67373056 75761663 8388608 4G Linux swap
/dev/sda4 75761664 976773134 901011471 429.7G Linux home

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The EFI partition is not formatted. For the sake of guaranteed replication, zero-fill it:

# dd if=/dev/zero of=/dev/sda1 bs=512

When the ubiquity GTK installer is launched, I select "something else" to manually assign and format the partitions.

The first partition is correctly detected as the EFI system partition, but the checkbox to format it is deselected and disabled.

After clicking "Install now" an error message appears indicating that it failed to mount /dev/sda1 to /boot/efi as vfat. It provides the option to "go back" or "continue".

By specification, the EFI system partition is required to be either FAT32, FAT16 or FAT12.

Here's the problem: If you go back, you cannot rectify the problem as there is no option to format the partition. If you continue, the installer will hang immediately after formatting the other partitions. It does not display an error - it just hangs indefinitely.

The error message is also a bit cryptic. An expert would realise there is a requirement to format the partition as vfat, but I suspect not many would know what they did wrong, or that they need to manually run "mkfs.vfat" to fix it.

TL;DR - the installer needs to do a better job of ensuring the EFI system partition is formatted as vfat.