[hatari-devel] Mini tutorial: Hatari and VHD hard disk images (and EmuTOS)

[Christian Zietz <czietz@xxxxxxx>]

Hi,

with Hatari, I semi-regularly need to run some programs from a HD image
instead of from a GEMDOS drive, to rule out any incompatibility of the
program with Hatari's GEMDOS emulation.

However, I always found it cumbersome to copy files to and from the HD
image. Of course, one can use mtools or Hatari with both the HD image
and a GEMDOS emulated drive, but I was looking for an easier (imho) way.

As I've just found out, Hatari can mount fixed-size(!) VHD (virtual HD)
images. This is not because of any particular support for that format
within Hatari, but because fixed-size VHD images are in fact just raw
images with some special magic values in the last 512 bytes. Any current
Windows version (iirc starting with Windows 7) can create these images
and mount them like an actual HD. (Sorry, Linux and Mac users! But you
can probably use a loopback device for that.)

Combine this with EmuTOS's capability of reading DOS partition tables
and FAT16 file systems and you can easily exchange data using that
image. (Atari TOS has much more restrictions regarding FAT16 settings.)

In case you want to use this as well, here is a mini tutorial.

Follow this guide to create a VHD file:
https://www.windowscentral.com/how-create-and-set-vhdx-or-vhd-windows-10
.... with the following exceptions:
- Create a VHD file, not a VHDX file.
- Select "Fixed size", not "Dynamically expanding".
- Be sure to initialize the disk with an MBR.
- Format any partitions that you create with FAT filesystem (not NTFS,
FAT32 or exFAT).

The guide also shows how to attach and detach a VHD image in Windows.
You can use it without any special options in Hatari (e.g. as ACSI
image) together with EmuTOS as long as it is currently
detached/unmounted from Windows.

Regards
Christian