Re: [Freedos-user] very small FAT12 partition?

[Steffen Grunewald]

On Sun, Jan 24, 2010 at 02:48:13PM +0100, Stefan Xenon wrote:
> Hi!
> My question is not exactly FreeDos related but I hope that you could
> help me anyway:
> 
> For an embedded project I need to create a very small FAT12 partition.
> In a proprietary project I found a partition of 4KB size (which I can
> not reuse because of license issues) but could not manage to recreate a
> similar one. Therefore on Linux I tried "mkdosfs -f 1 -F 12 -h 0 -S 512
> -C partition.iso 4" but it fails with the error message that this
> partition is too small. The smallest I could build this way was 34KB in
> size.

This may be a bit tricky, and require the use of non-standard tools, but
in theory it should be possible.

Don't forget about the general structure of floppy-based FAT filesystems.
You need:
- a boot block (MBR) containing a valid description of the FS (number and
        size of FAT[s], CHS geometry, etc. - not all of which can be tuned
        using standard tools probably) - "BIOS Parameter Block" is what
        you want to look for (and compare against actual values in a
        standard size floppy image)
- one or two FATs (starting with the magic code), big enough for your *data*
        blocks
- a root directory (size also fixed in boot block!)
- space for your data (and perhaps sub-directories which are data blocks
        themselves)

Apologies for being a bit vague, but I didn't use such stuff for a while,
but I've written down some details (& my notes are at home, unfortunately).


Steffen

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