Download a version of macOS using softwareupdate that will be downloaded to the /Applications folder.
softwareupdate --fetch-full-installer --full-installer-version 10.14.6
# Create a Catalina Virtual Disk Image
hdiutil create -o /tmp/Catalina -size 8500m -volname Catalina -layout SPUD -fs HFS+J
# Mount this Image to macOS
hdiutil attach /tmp/Catalina.dmg -noverify -mountpoint /Volumes/Catalina
# Use macOS Createinstallmedia Tool to create a Installer Image
sudo /Applications/Install\ macOS\ Catalina.app/Contents/Resources/createinstallmedia --volume /Volumes/Catalina --nointeraction
# Unmount Volume Catalina
hdiutil detach /volumes/Install\ macOS\ Catalina
# Convert the Catalina.dmg to a Catalina.iso for Virtual Machine
hdiutil convert /tmp/Catalina.dmg -format UDTO -o ~/Desktop/Catalina.cdr
# Move and Rename Catalina Image to Desktop
mv ~/Desktop/Catalina.cdr ~/Desktop/Catalina.iso
- https://www.virtualbox.org/
- https://www.oracle.com/virtualization/technologies/vm/downloads/virtualbox-downloads.html
- https://mjtsai.com/blog/2019/10/15/catalina-software-update-can-download-old-installers/
- https://www.techrepublic.com/article/how-to-use-snapshots-in-virtualbox/
- https://discussions.apple.com/thread/6135949#:~:targetText=Answer%3A%20A%3A,to%20VMware%20Fusion%20and%20Parallels
- https://github.com/myspaghetti/macos-guest-virtualbox
- https://techsviewer.com/install-macos-10-15-catalina-on-virtualbox-on-windows-pc/
- https://medium.com/@twister.mr/installing-macos-to-virtualbox-1fcc5cf22801