Making an ISO file from an Apple provided DMG file?

Question

I'd like to make a bootable ISO file from Apple-provided DMG file located under Download macOS using Safari on your Mac from: https://support.apple.com/en-us/HT211683. They provide a DMG file with a pkg file inside which I used xar -xf on, leading to a:

Distribution (exec, 9kb)
InstallMacOSX.pkg (pkg obviously, 6.21 GB)
Resources folder (650kb)

I'd assume InstallMacOSX.pkg is the most important, so it has these files:

Bom
InstallESD.dmg (6.2 GB)
PackageInfo
Payload (9 MB) (Renaming to .zip un'zips' a Install OS X El Capitan.app file)
Scripts

How would I utilize 'Payload' and 'InstallESD.dmg' to make a bootable ISO file?

Based off of this guide's end results, and my closest OSX version to this, I get these files:

.fseventsd
.IABootFiles (24.3 MB)
.IABootFilesSystemVersion.plist
.IAPhysicalMedia
Install macOS Sierra.app (5.03 GB)
Library
System (24.3 MB)
usr

Install macOS Sierra.app has: /Contents/SharedSupport/InstallESD.dmg (5.01 GB).

For what usage you want this iso? For create a VM under Virtualbox or an other virtualization software? — , Jul 09 '21 at 19:45
An iso is just a wrapper around bits. What do you hope consumes the ISO? — bmike, Jul 09 '21 at 20:28
Meh: You should edit your question and include what you are using the ISO for. This might generate answers with other alternatives. — David Anderson, Jul 09 '21 at 22:43
Virtualbox, or any VM honestly. Ironically I'm gonna try to run an older version of macOS on a mac. And yes, @david-anderson that does solve it. Thanks — Meh., Jul 10 '21 at 09:36
Meh: If the Install El Capitan with VirtualBox on OS X question and accepted answer did solve it, then you should upvote. This will indicate to others the value of that question and answer. — David Anderson, Jul 10 '21 at 15:03

score 1 · Answer 1 · answered Jul 09 '21 at 20:27

1

You can see this post : https://apple.stackexchange.com/a/420325/415185

I think you've only after the last instruction :

mv /tmp/Installer.dmg ~/Desktop

to add :

hdiutil convert ~/Desktop/Installer.dmg -format UDTO -o ~/Desktop/ElCapitan.iso
mv ~/Desktop/ElCapitan.iso.cdr ~/Desktop/ElCapitan.iso

And don't use the last instruction :

sudo asr restore .....

answered Jul 09 '21 at 20:27

Super great link to the Apple equivalent process to ISO on unix… – bmike Jul 09 '21 at 20:45

score 0 · Answer 2 · answered Jul 09 '21 at 20:04

Macos and OS X doesn’t boot from ISO but can boot from dragging the installer app to a flash drive on newer OS. Typically any processing you do adds steps, complexity for little benefit.

It’s usually easier to focus on which hardware (or era of hardware) you need and use the Apple app to install onto a USB drive and have the installer there and use the startup manager to select and run things.

Making an ISO file from an Apple provided DMG file?

2 Answers2