How to Create Bootable MacOS Catalina.ISO and .DMG images in both MacOS and Windows

How to Create Bootable MacOS Catalina.ISO and .DMG images in both MacOS and Windows

This quick instruction will help any-one to make a Bootable MacOS Catalina Installer.ISO and .DMG images in MacOS and Windows.

MacOS Catalina.ISO is needed for installing Catalina into a virtual machine using VMWare and Virtual box and other purposes.

How to create a Bootable MacOS Catalina.ISO image on a Mac?

Step 1: Download MacOS from App Store into Applications folder.
From your MacOS, it’s easy to download the official Install macOS from App Store into the Applications folder by just use the upgrade function (Apple Logo > About This Mac > Software Update…).

In the case you are using Catalina already, download the Install macOS from this topic, then move it into Applications folder.

Step 2: Open Terminal (found in Applications/Utilities/), the enter the following command lines:

  • Firstly, Create a 8900 MB DMG Disk Image

hdiutil create -o /tmp/Catalina -size 8900m -volname Catalina -layout SPUD -fs HFS+J

Make sure that your Mac still has at least 9Gb of Free disk space to avoid unexpected issues.

  • Then, Mount it to your macOS

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

  • Next, Create macOS Catalina Installer

sudo /Applications/Install\ macOS\ --volume /Volumes/Catalina --nointeraction

  • Next, Unmount Catalina Disk

hdiutil detach /volumes/Install\ macOS\ Catalina\

And now we have Bootable MacOS Catalina.DMG image (/tmp/Catalina.dmg). To download this file, go to this topic.

How to get the ISO file? Take the following further steps:

  • Next, Convert the dmg file to a iso file

hdiutil convert /tmp/Catalina.dmg -format UDTO -o ~/Desktop/Catalina.cdr

  • Lastly, Rename and Move to Desktop

mv ~/Desktop/Catalina.cdr ~/Desktop/Catalina.iso

Finally we get the Catalina.iso image in the Desktop.

We uploaded and share this file through this topic.

How to make a Bootable MacOS Catalina.ISO image in Windows 10?

Step 1: Download the official MacOS Catalina 10.15.0.DMG from here.
Step 2: It’s pretty easy and simple to Convert MacOS Catalina 10.15.0.DMG to MacOS Catalina 10.15.0.ISO in Windows using many available Free tools such as Dmg2img or Anyburn.

  • How to use Dmg2img?
    After downloading and unzipping the file, the usage in a DOS box is simple.
    For DMG to ISO:

dmg2img example.dmg example.iso

  • How to use Anyburn?

Unfortunately there will be boot error and installation never succeed. Used macOS 10.15.1 at November 25, 2019 and VirtualBox 6.0.14 directly in new iMac (original Apple hardware).
Also unmounting hdiutil detach /Volumes/Install\ macOS\ Catalina\ will fail. Perhaps last slash to remove?

To get Catalina installed successfully into Virtual Box, you should visit this topic: Instruction to Install macOS 10.15 Catalina on VirtualBox on a Mac