How to cancel Ventura installation?

So, like many other people, I've just been bitten by the Ventura update being a straight-up immediate installation instead of just downloading an install app that I can then use to install inside a Parallels VM. Fortunately, I had an app open that had a modal window active, which prevented the system from actually rebooting, so I haven't actually installed a beta OS on my production machine. However, the /System/Volumes/Update/mnt1 volume is still there on /dev/disk1s1, even after I reset the profile to the default in the Software Update prefpane, and I'm worried that I'm destined to install this the next time my machine restarts.

Is there any way to get rid of this, so that it doesn't install the beta the next time I have to reboot my machine for some random reason?

Okay, so for the benefit of the next person who runs into this, here's the steps I ended up using to defuse this:

  1. Download and run the Monterey 12.4 installer.

  2. Select the hard disk for the installation.

  3. When the installer displays the progress bar with 30ish minutes remaining, it's setting up the install partition, and thus overwriting the one that Ventura set up.

  4. Click Cancel in the installer.

  5. Check less /System/Volumes/Update/mnt1/System/Library/CoreServices/SystemVersion.plist to make sure the partial boot partition has an incomplete 12.4 on it, and not 13.0 anymore.

  6. Reboot. Hold your breath while the system tries to install the OS.

  7. Since the boot partition was incomplete, I arrived at my usual Monterey 12.4 setup, with the boot partition having apparently been deleted, and all well other than the hours I spent trying to avert disaster.

Not Cool, Apple. Don't trick users into accidentally installing a beta OS.

Thanks for this! Luckily like you, I was able to catch it before the install started while watching the initial download complete. As soon as it went to "Preparing" I got worried, but thought maybe, just maybe an installer window would appear soon. My heart sunk when "Restart to install" appeared. Quickly canceled the restart, and searched for options to clear the install. Your solution is quick and easy.

Yes, many thanks. It's good to know I'm not the only one caught out.

It leaves me wondering: is it possible to create a Ventura beta install drive ? If so, how ? I can't find the Ventura installer anywhere. Also, is there a way to get the Ventura beta into a VM ? I've tried but my Parallels VM refuses to sign in with my Developer Apple ID.

How are we expected to test betas if we can't install them safely ?

I have sent Apple a (polite) roast via "Feedback Assistant". Maybe someone will read it.

How to cancel Ventura installation?
 
 
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