This is a small addendum to my main article on how to install macOS in a VM, which I'll keep as-is as that's effectively the normal way. But, if you'd like to jump on the fresh-off-the-press public release of Big Sur, here's what you have to do to make that work right now.

I'm sure the relevant repositories will be updated shortly, but this will help you get to a running VM right now, and the process itself is useful to follow whenever you want to install a newer version after already having installed an earlier version, for example.

With this in mind, please consider this an addendum to the main article, so use them alongside one another.

Step 1: Remove previously downloaded files

If you have previously already downloaded (or attempted to) earlier versions, let's start by deleting these files. Open up a Terminal window where you have checked out the OSX-KVM repository, and let's clean things up:

# Delete previously downloaded catalog files
rm -rf content/catalogs;

# Delete previously downloaded installer files
rm {BuildManifest.plist,Info.plist,InstallAssistant.pkg,InstallInfo.plist,MajorOSInfo.pkg}

# If you have followed my guide previously, delete all files in your extracted folder too
rm -rf extracted/*

Step 2: Modify one line in fetch-macOS.py

The as-of-the-posting-of-this-article current version of fetch-macOS.py refers to the DeveloperSeed catalog by default. We'll simply change this to point to PublicRelease. Open fetch-macOS.py in your favorite text editor, and look for lines :77-78. Comment-out the developer seed one, and uncomment the public release one that should already be there. If it isn't, you can add it yourself:

def get_default_catalog():
    '''Returns the default softwareupdate catalog for the current OS'''
    return catalogs["PublicRelease"]
    #return catalogs["DeveloperSeed"]
Note: This works the other way around too, of course. Should the script from the OSX-KVM repository be updated to have PublicRelease as the default, for example, you can switch to DeveloperSeed to get the recent-most developer build.

That's all you'll need to change here. Save, close, and done. You can now run the script to download the recent-most public release of macOS Big Sur:

./fetch-macOS.py --big-sur

Step 3: Continue as normal

You can now continue with the setup and installation process the same way as before, so head on over to the main article and follow its remaining steps.

Enjoy!