Re: MFS Filesystem support

[Josh Juran <jjuran@gmail.com>]

On Apr 14, 2024, at 7:07 PM, The Mariocrafter <kayvonkamyar@gmail.com> wrote:

> Macintosh File System (MFS) is a filesystem used in early Macintosh
> models up to those running System 3, when the original HFS (which is
> supported within Linux) supported it.  Although no Mac model that
> shipped or can run with an MFS-only macOS can run Linux, floppy disks
> formatted with an MFS system may still exist and the user never
> bothered to reformat it to HFS or HFS+,

Mac OS never provided a facility for formatting 400K disks as anything but MFS.

> and the main use case I can
> think of is using MFS to transfer files from a modern device to a Mac
> that does not support HFS.

This would require a read-write implementation of MFS.  By the way, are we talking disk images for e.g. Mini vMac, or actual 1980s hardware?

> It would be nice supporting the MFS
> filesystem natively within Linux, which could be read-only or
> read-write.

An alternative to native filesystem support is to read and write disk images in userspace.  Aside from not increasing the kernel’s attack surface or imposing a licensing constraint, it has the benefit of being portable to other operating systems.

For example, I created a (so far) read-only implementation of MFS for Advanced Mac Substitute[1] (an emulator plus reimplementation of Mac OS for running 68K applications).

https://github.com/jjuran/metamage_1 (see 68k/modules/ams-fs/MFS.cc)

If someone does seek to implement MFS, at the very least you might find the comments useful.

Cheers,
Josh

[1] https://www.v68k.org/ams/