Unable to create the installation medium - Sierra Host, High Sierra Guest

[skymoo]

Just updated to Fusion 10.0.1 and I'm trying to setup a High Sierra Guest on my Sierra machine. On installation I get an error stating that it's "Unable to create the installation medium".

I recall seeing something similar with Fusion 8 and the Sierra developer previews, but as High Sierra is apparently supported as I guest I'm surprised that I'm getting this error.

How do you install a High Sierra Guest, before I installed a Sierra Guest and then upgraded but surely that should no longer be necessary.

[OriginalSix]

You should be able to download high Sierra from App Store.  Exit the installation.  Then use the 'Install High Sierra' application as your installation media for your VM guest.

[skymoo]

That's what I've been trying to do, when using that at the installation media I get the error about being unable to create the installation medium.

[ColoradoMarmot]

Just drag the installer to the easy setup wizard.  If it still doesn't work, then it's likely you have an older high sierra installer - which only included part of the install media.  The current installers have the full set of files.  5.17/5.18 GB.

[skymoo]

That must have been the problem as after deleting the "Install macOS High Sierra" app and redownloading from the AppStore allowed me to install a VM.

[dvdtoth]

In case someone else hit the same problem. Host High Sierra, guest High Sierra I was still getting the same 'Unable to create the installation medium' message.

I had to move the High Sierra installer from /Applications to my home folder, drag it from there to the wizard and the VM installed that way.

[Anonymous]

Wow, dvdtoth, I don't know how you figured that out, but it's genius. Who'd a thunk?!

[r34z1n]

Beautiful! I had just upgraded Fusion solely to clone High Sierra and was running into errors. Your fix worked flawlessly! Thanks!

[RobertBou]

Be sure you don't already have Install ESD mounted.

(Use Disk Utility or other methods to be sure)

[mklement]

Dragging the installer *.app bundle of out /Applications, as dvdtoth recommend above, is an excellent workaround. It is also necessary in VMWare Fusion 11.5 with the official macOS Catalina (10.15) installer, at least with macOS 10.14.6 as the host OS.

[TotalUnderpass]

This did it for me.  On 10.14.6 installing Catalina 10.15.2 onto a Fusion VM.  Open Disk Utility and unmount InstallESD.dmg.

[rbodgers]

(Note: this reply is regarding macOS Catalina host and guest)

This ended up being my solution.

After downloading the installer, the installer automatically launches (and presumably mounts the `Install ESD.dmg`.  Quitting the installer was not sufficient to unmount that image, at least in my case.