Typically the resulting installer ISO files are used for installing macOS into virtual machines like VMWare or VirtualBox, but they can also be used to burn the ISO to media to create a boot disk.

This offers an alternative to creating a bootable USB flash drive for MacOS installers as well.

You can use the same steps to create an ISO file from practically any other MacOS Installer with createinstallmedia present however, including building a MacOS Catalina ISO, or for Big Sur, High Sierra, and Sierra, simply by replacing the file names where appropriate.

You can also convert ISO files to VDI VirtualBox images if needed.

Either way, when, at Step 6, createinstallmedia tries to erase the disk it fails: Error erasing disk error number (22, 0).

My work around is just to open disk utility or find it on the desktop and manually detach it.

It seems it worked with Sebby tip and your instructions.Thanks.

But the articles really help me understand the MacOS and fix issues or make changes.

In step 4 you Create a disk image DMG file that you later mount to create the installer app on and then you unmount the disk image.

This is common practice in technical and scientific articles to help the readers.

You can create an image, partition it and put a filesystem in it, in the right image format, all in one step: hdiutil create -size 10g -type UDTO -layout SPUD -fs JHFS Desktopsomething.cdr open Desktopsomething.cdr.

You might want to check your mask, it may be too tight:) Thanks for the article.

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Disk Image File To Iso