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.