Is there a way to convert the existing VM images to ASIF?

[wattachai]

I'm very interested in the new Apple Sparse Image Format (ASIF) support as described in #530, which I believe it's been included in the 2.1 release.

It seems there is a way to convert an existing disk image to ASIF format according to https://eclecticlight.co/2025/06/12/macos-tahoe-brings-a-new-disk-image-format/

Currently, there are only two ways to create one of these new disk images, either in Tahoe’s Disk Utility, or using its diskutil command tool, as in
diskutil image create blank --format ASIF --size 100G --volumeName myVolume imagePath
to create an ASIF image with a maximum capacity of 100 GB with a single APFS volume named myVolume with the path and name imagePath. You can also use a from option to convert an existing disk image to ASIF format.

My concern is the compatibility with vbvm created by VirtualBuddy. Would simply using diskutil to convert Disk.img inside vbvm does the job correctly?

PS. kudos to your continuous development effort on VirtualBuddy!

[insidegui]

I'm not sure if this will work for existing boot disk images. You could try duplicating a VM and converting the disk image, maintaining the same file name, just to see if it will still boot. If we find out that it's possible I may add this option to convert existing images in a future update.

[wattachai]

Unfortunately, it didn't work 🥲. Creating a new VM with ASIF (most efficient) is not going well for Tahoe guest either. I got stuck at preparing installation step.

Update: I could successfully create a new VM with ASIF by choosing Sequoia 15.6.1 instead of Tahoe 26.0. This could be a Tahoe-guest specific issue.

[Kurville]

I'm on macOS 26.0.1. I used Disk Utility (not the Terminal) to convert the Disk.img file to ASIF.

After, I was looking for a setting to point the location of the ASIF file to replace the IMG, but I couldn't find one. So I renamed the ASIF with the ".img" extension and I was able to launch the virtual machine (macOS 12.7.6).

The ASIF file is about 10 GB smaller than the original IMG.