multiple operating systems

Kelly Burgess kellyb at
Tue Sep 21 05:05:34 UTC 2021

Hi Grant,

Just a couple of things to add...

I use VMWare Fusion, and I have a set of VMs similar to what Doug listed for his Parallels setup.  Each time I do a new MacOS install, I quit the installer when it comes up, make a backup copy of it, then re-run it to do the install (because the installer is deleted automatically after it finishes).  I use the backup installers to upgrade older Macs for friends when e.g. El Capitan is no longer available to their Macs via Software Update.  The catch is that when you run an old installer, it will usually complain about being corrupted.  The real cause of that is a failure to validate the expired certificate it was built with.  The solution is to change the system clock on the target Mac to the year that the installer was built.  Then the 'corrupted' installer will work fine.

Another way to create a VM with Fusion is by imaging a working boot drive that runs the OS you want to turn into a VM.  I posted about that here -


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