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When formatting my EFI partition I get this error:

Not enough clusters for a 32 bit FAT!"

My disk use 4096 sector size.

#mkfs.fat -v -F 32 -S 4096 /dev/sde1 mkfs.fat 4.1 (2017-01-24) WARNING: Not enough clusters for a 32 bit FAT! /dev/sde1 has 255 heads and 63 sectors per track, hidden sectors 0x4000; logical sector size is 4096, using 0xf8 media descriptor, with 67584 sectors; drive number 0x80; filesystem has 2 32-bit FATs and 8 sectors per cluster. FAT size is 16 sectors, and provides 8440 clusters. There are 32 reserved sectors. Volume ID is 05deb9f7, no volume label.

My disk partition:

gdisk -l /dev/sde GPT fdisk (gdisk) version 1.0.1 Partition table scan: MBR: protective BSD: not present APM: not present GPT: present Found valid GPT with protective MBR; using GPT. Disk /dev/sde: 244190646 sectors, 931.5 GiB Logical sector size: 4096 bytes Disk identifier (GUID): D0BA102E-86C5-4379-B314-9534F873C377 Partition table holds up to 128 entries First usable sector is 6, last usable sector is 244190640 Partitions will be aligned on 256-sector boundaries Total free space is 244123051 sectors (931.3 GiB) Number Start (sector) End (sector) Size Code Name 1 2048 69631 264.0 MiB 0700 EFI_FAT32

fsck.fat give the following:

#fsck.fat -v /dev/sde1 fsck.fat 4.1 (2017-01-24) Checking we can access the last sector of the filesystem Warning: Filesystem is FAT32 according to fat_length and fat32_length fields, but has only 8440 clusters, less than the required minimum of 65525. This may lead to problems on some systems. Boot sector contents: System ID "mkfs.fat" Media byte 0xf8 (hard disk) 4096 bytes per logical sector 32768 bytes per cluster 32 reserved sectors First FAT starts at byte 131072 (sector 32) 2 FATs, 32 bit entries 65536 bytes per FAT (= 16 sectors) Root directory start at cluster 2 (arbitrary size) Data area starts at byte 262144 (sector 64) 8440 data clusters (276561920 bytes) 63 sectors/track, 255 heads 16384 hidden sectors 67584 sectors total Checking for unused clusters. Checking free cluster summary. /dev/sde1: 1 files, 1/8440 clusters
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A FAT32 filesystem has a minimum size: it should contain at least 65525 clusters*. The cluster size is a multiple of the sector size. In your case the sector size is 4096 and mkfs.vfat has used a default multiple of 8 for the number of sectors per cluster. Use -s 1 to specify one sector per cluster:

mkfs.fat -v -F 32 -S 4096 -s 1 /dev/sde1

This results in a cluster size of 4096, which should be small enough to fit more than the minimum of 65525 clusters in your 264 MiB partition.

* From the Windows documentation on UEFI/GPT-based hard drive partitions:

For Advanced Format 4K Native drives (4-KB-per-sector) drives, the minimum size is 260 MB, due to a limitation of the FAT32 file format. The minimum partition size of FAT32 drives is calculated as sector size (4KB) x 65527 = 256 MB.

Advanced Format 512e drives are not affected by this limitation, because their emulated sector size is 512 bytes. 512 bytes x 65527 = 32 MB

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    With FreeBSD it it is not -s, but -c as in newfs_msdos -F32 -S 4096 -c 1 -L boot02 /dev/ada0p1. Commented Mar 27, 2021 at 15:28

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