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How to Create a Bootable macOS Big Sur ISO

This tutorial shows you how to create a bootable macOS ISO. The ISO can be used to create a DVD to install macOS on different Mac hardware or you can use the ISO to create a macOS virtual machine.

Before we begin

In order to create the ISO you need to download the full macOS installer app to your Applications folder. The following tutorial shows you how.

Once, you’ve downloaded the macOS installer, follow the steps below to create the ISO.

Instructions

Open the Terminal app by pressing Command + Space, searching for “Terminal” then pressing Return.

Create a temp disk image by executing the following command.

hdiutil create -o /tmp/macOS -size 12945m -volname macOS -layout SPUD -fs HFS+J

Mount the temp disk image with the following command.

hdiutil attach /tmp/macOS.dmg -noverify -mountpoint /Volumes/macOS

Use the createinstallmedia utility (located inside the Install macOS Big Sur app) to copy the installer files to the mounted disk image by running the following command.

sudo /Applications/Install\ macOS\ Big\ Sur.app/Contents/Resources/createinstallmedia --volume /Volumes/macOS --nointeraction

Enter your password when prompted and wait the files to copy. Once the copying has finished we can unmount the temp disk image with the following command.

hdiutil detach -force /Volumes/Install\ macOS\ Big\ Sur

Convert the macOS disk image to an ISO file by executing the following commands.

hdiutil convert /tmp/macOS.dmg -format UDTO -o ~/Desktop/macos-big-sur
mv ~/Desktop/macos-big-sur.cdr ~/Desktop/macos-big-sur.iso

Conclusion

The macOS Big Sur bootable ISO should now be created and stored on your Desktop. You can test the ISO by using it to create a macOS virtual machine with VMware Fusion or burning it to DVD and using it on another Mac.