Extract ISO image from macOS Somona installer

macos-iso.md

Extract ISO Image from a macOS installer

Step 1

Download macOS Installer (InstallAssistant.pkg). Here is the link to Sonoma beta installer:

https://swcdn.apple.com/content/downloads/14/54/042-41491-A_WCZEM7L2US/b5eeeylcnmf82ycto51pvy0klcyzd02on8/InstallAssistant.pkg

Step 2

Run InstallAssistant.pkg by double-clicking on it. This will move Install macOS Sonoma beta.app to /Applications folder.

Step 3

Create a new DMG file, open Terminal and run:

hdiutil create -o /tmp/Somona -size 16000m -volname Somona -layout SPUD -fs HFS+J

The above command will create a 16GB DMG file called Somona in /tmp folder

Step 4

Mount the DMG file we just created:

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

Step 5

Use createinstallmedia to create the macOS installer on the mounted volume:

sudo /Applications/Install\ macOS\ Sonoma\ beta.app/Contents/Resources/createinstallmedia --volume /Volumes/Somona

Step 6

Unmount the volume we've just created:

sudo hdiutil detach /Volumes/Install\ macOS\ Sonoma\ beta

Step 8

Convert the DMG disk image file to an ISO disk image file (technically a CDR file):

sudo hdiutil convert /tmp/Somona.dmg -format UDTO -o ~/tmp/Somona.cdr

Step 9

Finally rename the CDR file to ISO:

sudo mv ~/tmp/Somona.cdr ~/tmp/Somona.iso

Links & Resources

https://macpaw.com/how-to/create-iso-file

https://osxdaily.com/2020/07/20/how-convert-macos-installer-iso/

Step 5 opens a file called createinstallmedia. The pathway to that file may vary depending on which version of InstallAssistant.pkg you download.
This path:
sudo /Applications/Install\ macOS\ Sonoma.app/Contents/Resources/createinstallmedia
works for the InstallAssistant.pkg downloaded from the link in Step 1.

You can also get to it this way:
sudo "/Applications/Install macOS Sonoma.app/Contents/Resources/createinstallmedia"
which does not look all mangled with the two escape characters as seen in the first line.

The best way to get to createinstallmedia is to use your tab key to autocomplete commands, like this:
sudo /App[TAB]/In[TAB]/Con[TAB/]Re[TAB]/crea[TAB]

Yes, step two is a funny one to try to explain. You just have to know to step through the install procedure until the "Install macOS Sonoma.app" file is copied to the Application folder.

BTW I use iTerm2 instead on MacOS terminal.

Some of "Sonoma" is wrongly written "Somona". I got an error and wondered why for few seconds.

June 10 2024 update:

Step 3 now requires 16250m instead of 16000m to fit the macOS 15 Sequoia beta

Here is the updated tutorial:

Extract ISO Image from a macOS installer

Step 1

Download macOS Installer (InstallAssistant.pkg). Here is the link to Sequoia beta installer:

https://swcdn.apple.com/content/downloads/50/33/052-49060-A_SUZPTRSXUG/rshd6um52uzcxnr1u85utqhl124vmsph1c/InstallAssistant.pkg

Step 2

Run InstallAssistant.pkg and go through the installer. This will move Install macOS 15 beta.app to /Applications folder.

Step 3

Create a new DMG file, open Terminal and run:

hdiutil create -o /tmp/Sequoia -size 16250m -volname Sequoia -layout SPUD -fs HFS+J

The above command will create a 16GB DMG file called Sequoia in /tmp folder

Step 4

Mount the DMG file we just created:

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

Step 5

Use createinstallmedia to create the macOS installer on the mounted volume:

sudo /Applications/Install\ macOS\ 15\ beta.app/Contents/Resources/createinstallmedia --volume /Volumes/Sequoia

Step 6

Unmount the volume we've just created:

sudo hdiutil detach /Volumes/Install\ macOS\ 15\ beta

Step 7

Convert the DMG disk image file to an ISO disk image file (technically a CDR file):

sudo hdiutil convert /tmp/Sequoia.dmg -format UDTO -o ~/Sequoia.cdr

Step 8

Finally rename the CDR file to ISO:

sudo mv ~/Sequoia.cdr ~/Sequoia.iso

Links & Resources

https://macpaw.com/how-to/create-iso-file

https://osxdaily.com/2020/07/20/how-convert-macos-installer-iso/

It is also recommended to use some kind of virtual Mac for this if you don't have a real Mac.

$ diskutil resizeVolume "/Volumes/Install macOS Sequoia" limits
Resize limits for partition disk2s7 (Sequoia):
  Current partition size on map:             19.9 GB (19935526912 Bytes)
  Current container size:             	      19.9 GB (19935526912 Bytes)
  Minimum (constrained by file usage):       16.1 GB (16073895936 Bytes)
  Recommended minimum (if used for macOS):   19.9 GB (19935526912 Bytes)
  Maximum (constrained by map space):        19.9 GB (19935526912 Bytes)

Sequoia (15.1.1) Minimum (constrained by file usage): 16.1 GB