DOS FAT12/16/32 filesystem

The limits for DOS FAT12/16/32 filesystems include:

Filename length

255 characters.

Pathname length

1024 characters, not including the mountpoint or the terminating NUL.

File size

4 GB − 1; uses a 32-bit filesystem format.

Directory size

Depends on the type of filesystem:

• The root directory of FAT12/16 is special, in that it's pregrown and can't increase. You choose the size when you format, and is typically 512 entries. FAT32 has no such limit.
• FAT directories are limited (for DOS-compatability) to containing 64 K entries.
• For long (non-8.3) names, a single filename may need multiple entries, thus reducing the possible size of a directory.

Filesystem size

Depends on the FAT format:

• for FAT12, it's 4084 clusters (largest cluster is 32 KB, hence 128 MB)
• for FAT16, it's 65524 clusters (thus 2 GB)
• for FAT32, you get access to 268435444 clusters (which is 8 TB)

Disk size

Limited by the disk driver and io-blk.

These filesystems don't really support permissions, but they can emulate them.