How to Properly Enlarge A VM's Virtual Disk in Fusion?

[SnakeGirl]

What is the correct procedure for allocating more disk space to a VM that has already been created in Fusion (for example if i want to upgrade a Guest OS VM to a later version but there isn't enough disk space in the VM to be able to do the upgrade)?  Can disk space be added after the VM has been created & the Guest OS installed or does the virtual disk need to be made a large enough size before installing the initial Guest OS?

[Technogeezer]

You’ll first expand the virtual disk size in Fusion. From ther it gets a bit murky because you’ll have to use macOS tools to resize things. But for a boot disk that will involve using Disk Utility by booting to macOS Recovery or using a bootable macOS installer disk. Disk Utility doesn’t seem to want to resize the boot drive of a running macOS system.

The process is also different depending on what macOS you’re running as there are differences in boot disk layouts. Which macOS version are you interested in? 

[SnakeGirl]

Well, the Guest OS VM is macOS High Sierra (10.13) & i would like to attempt to upgrade it to Catalina (10.15) but in the initial installation/upgrade process, it said i needed 10 more GB so i enlarged the High Sierra VM disk size from 40 GB to 60 GB in the VM settings (this is Fusion 10).  But in Disk Utility in the VM, it still looks like it doesn't recognize the additional 20 GB & still thinks it is 40 GB so i wasn't sure what you have to do to configure it properly so that everyone across the board recognizes that the disk size is now 60 GB & not 40 GB.

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