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FAT32 drive on GPT (Miscellaneous)

posted by bretjohn Homepage E-mail, Rio Rancho, NM, 02.09.2023, 03:39

> For GPT entries, there is no distinction between FAT and NTFS partitions.
> Both have partition type EBD0A0A2-B9E5-4433-87C0-68B6B72699C7.
In GPT, these are all classified as "Microsoft Basic Data" (which also covers exFAT). Even though there are plenty of bits to distinguish between the various partition types (way more than the single byte provided by MBR) MS decided for some reason to ignore that capability.

> If the non-FAT partitions do not get a drive letter assigned at boot, there
> is no way to reformat a such partition under FreeDOS with a FAT filesystem,
> at least with the format utility currently provided by FreeDOS.
>
> Perhaps this behaviour should be configurable?
In my USB program, by default it only assigns drive letters to compatible (FAT-formatted) partitions. To identify what's in the partition, though, it can't use the GPT entry. It must look at the data in the first sector (volume boot record) of the partition to see what's actually there (if anything).

This is different than MBR, where you can (at least theoretically) tell how a partition/volume is _supposed_ to be formatted (even if it hasn't yet been formatted) by the partition type value in the MBR.

The USB program also has a command-line option to mount non-compatible partitions (like NTFS or exFAT or non-formatted partitions) as drive letters so they can (at least theoretically) be (re)formatted by a DOS program. Of course, that's a dangerous thing to do unless you're _really_ sure you know what you're doing.

It seems like it might also be possible to create a FORMAT program that doesn't require a drive letter as input. I know there are some partition managers that will format the partitions they create (FDISK doesn't do that). Maybe that's the better approach, but it seems like it would also be possible to create a "smarter" FORMAT program that could make up for some of the shortcomings in FDISK?

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