Format FAT32 partition with set "Allocation Unit Size"

Note: This answer didn't work for me.

I wish to format a FAT32 partition with set AUS of 32K. I've read the man page man mkfs.fat, and the only thing that I can find is

-S LOGICAL-SECTOR-SIZE Specify the number of bytes per logical sector. Must be a power of 2 and greater than or equal to 512, i.e. 512, 1024, 2048, 4096, 8192, 16384, or 32768.

I don't know whether this is the "AUS", but I tried it out, and set -S 32768. This happened:

user@pc:~$ sudo mkfs.fat -S 32768 /dev/sdb1
mkfs.fat 3.0.28 (2015-05-16)
Warning: sector size is set to 32768 > 4096, such filesystem will not propably mount
WARNING: Not enough clusters for a 32 bit FAT!
mkfs.fat: Attempting to create a too large filesystem

I also tried sudo mkfs.fat -I -S 32768 /dev/sdb if that works, and it doesn't. Same error prints out.

2 Answers

man mkfs.fat:

-s SECTORS-PER-CLUSTER Specify the number of disk sectors per cluster. Must be a power of 2, i.e. 1, 2, 4, 8, ... 128.

The allocation unit size is also known as the cluster size.

The best way is to divide by 512 (the cluster size):

mkfs.fat -S $((32768/512)) /dev/sdb1