The steps allowing to create macOS 10.15 Catalina VM on vSphere or ESXi

Catalina_ISO.sh

#!/bin/bash

# Steps to create the macOS Catalina (10.15) VM:
# login to developer.apple.com or beta.apple.com to download a tester's profile for your OS. Install it.
# Go to System Preferences > Software Update and start the update process
# When the Catalina Installer (few MBytes) is started, it downloads the remain part of installation.
# After all `Install Catalina Beta.app` should lay in the /Applications folder with approx. 6.5g size
# Proceed with the following script.

set -eux

mkdir -p out

sudo hdiutil create -o out/Catalina.cdr -size 7g -layout SPUD -fs HFS+J
sudo hdiutil attach out/Catalina.cdr.dmg -noverify -mountpoint /Volumes/install_build
sudo /Applications/Install\ macOS\ Catalina\ Beta.app/Contents/Resources/createinstallmedia --volume /Volumes/install_build --nointeraction
hdiutil detach /Volumes/Install\ macOS\ Catalina\ Beta
hdiutil convert out/Catalina.cdr.dmg -format UDTO -o out/Catalina.iso
mv out/Catalina.iso.cdr out/Catalina.iso
rm out/Catalina.cdr.dmg

# Now there should be an ISO called Catalina.iso in the `out` folder
# Upload the resulted ISO to vSphere datastore (upload to an ESXi host)
# Create a new VM as Guest OS set to `Other:Apple macOS 10.14 64-bit`. Don't start a VM
# Then compatibility should set to `ESXi 6.7 update 2 and later` and Guest OS to `Windows 10 64-bit`
# Start the VM, make sure that CDROM with datastore ISO (Catalina.iso) is connected
# Disable the Network boot option in vSphere BIOS menu. Restart VM
# Installer should start. You should choose Disk Utility, and initialize the VMware Virtual SATA Hard Drive Media
# (since keyboard ain't work - using existing `Untitled` name)
# Wait util installer completes. VM will not boot. Shutdown VM, change Guest OS profile back to `Other:Apple macOS 10.14 64-bit`
# Once Catalina is installed, download the latest VMware tools and install it.
# It took two reboots for me to completion (will require to unblock security extension)

# Credits to Intel008 and Bogdam from https://communities.vmware.com/thread/611961
# Credits to mkuzmin https://github.com/jetbrains-infra/packer-builder-vsphere/blob/master/examples/macos/setup/iso-macos.sh
# Credits to pat-s https://gist.github.com/agentsim/00cc38c693e7d0e1b36a2080870d955b

@Kutkovsky Thank you for sharing! This works great for the released version of Catalina after increasing size from 7g to 9g

The released version of Catalina I downloaded is 8.1GB in size.

sudo hdiutil create -o out/Catalina.cdr -size 9g -layout SPUD -fs HFS+J

The resulting Catalina.iso was 9.66GB in size

-rw-r--r--   1 edward3  staff  9663676416 Oct 24 08:43 Catalina.iso

I need to update my ESXi host before I can try it out.

Is 6.7 version of ESXi a mandatory requirement? I've gone through a similar procedure on ESXi 6.5. The install successed without problem, but the installed vmdk cannot boot after changed OS Profile back to macOS. Will try to upgrade 6.7 later..

Thanks worked on 6.7U3
But where can I find darwin.iso proper for this?
(Hardware I use is: MacPro6.1)

But where can I find darwin.iso proper for this?

use the darwin.iso from VMware Fusion - it's the same VMware Tools. Don't use the darwinPre15.iso - it's for versions 10.10 and earlier.