How to Make a MacOS Big Sur ISO File
Some advanced users may wish to create an ISO file of the macOS Big Sur installer file (or MacOS Catalina installer, or MacOS Mojave installers for that matter). These can be useful for installing MacOS into virtual machines like VirtualBox and VMWare, and because the resulting installer is an ISO file it can be helpful for creating an alternative installer media whether on an SD Card, external hard drive, USB flash key, or similar, especially when the typical approach to creating a bootable USB installer drive for MacOS Big Sur is not viable or possible.
Because the macOS installer application is an .app file and do not arrive as a disk image, to create a MacOS ISO file requires a sequence of steps through the command line, or the use of a third party application. For the purposes here, we’ll walk through how you can make a MacOS Big Sur ISO file by using the terminal.
How to Create a MacOS Big Sur ISO File
We will be focusing on making an ISO file for macOS Big Sur, but you can use this same approach for making an ISO file of MacOS Catalina and macOS Mojave too.
- Get the MacOS Installer application that you wish to use:
- For MacOS Big Sur, macOS Catalina and MacOS Mojave, go to the Mac App Store (or use this method to download full macOS installers) and download the installer applications for the macOS version you wish to make an ISO file of
- The MacOS installer app should be in the /Applications folder and be labeled as “Install macOS Big Sur.app” or similar, keep it there and make note of the file name
- Next launch the Terminal application by hitting Command+Spacebar and typing “Terminal” and hitting the return key, or by launching it directly from the Utilities folder
- First, we must create a temporary disk image:
- Next, mount the disk image:
- Now we’ll use the createinstallmedia utility that is part of the MacOS Installer application to copy the installer files to the disk image you just created:
- Hit return and enter the admin password to authenticate, let this process complete as it makes the installer that will turn into the ISO. When finished, we then unmount the disk image volume:
- Next, we’ll convert the freshly created MacOS Installer disk image file to a CDR / ISO file that will appear on the desktop:
- Finally, we change the file extension from .cdr to .iso:
hdiutil create -o /tmp/MacBigSur -size 12500m -volname MacBigSur -layout SPUD -fs HFS+J
hdiutil attach /tmp/MacBigSur.dmg -noverify -mountpoint /Volumes/MacBigSur
sudo /Applications/Install\ macOS\ Big\ Sur/Contents/Resources/createinstallmedia --volume /Volumes/MacBigSur --nointeraction
hdiutil detach /Volumes/MacBigSur/
hdiutil convert /tmp/MacBigSur.dmg -format UDTO -o ~/Desktop/MacBigSur.cdr
mv ~/Desktop/MacBigSur.cdr ~/Desktop/BigSur.iso
Assuming you completed the steps properly, you should now have an ISO file called MacBigSur.iso on the Mac desktop. This is basically a variation of converting an installer to ISO as discussed here, which you may have some familiarity with already.
The resulting macOS Big Sur ISO file can now be used to install macOS Big Sur into various virtual machines including VirtualBox and VMWare, and it can also be used to burn to various media including Blu-Ray, SD Cards, external hard drives, and USB Flash drives.
For what it’s worth, you can also convert dmg and cdr files to ISO with Disk Utility too, but the terminal approach to converting dmg to ISO and vice versa with hdiutil is long established and works well, and since you’re already in the command line anyway for working with the createinstallmedia utility the whole process may as well stay in the Terminal.
Obviously this is specifically for if you need to create a MacOS installer ISO file for whatever reason, but it’s worth pointing out that this is not necessary if you simply want to create boot disk USB Installer for macOS Big Sur beta (or final), boot installers for MacOS Catalina, or for MacOS Mojave, all of which are possible by using the createinstallmedia commands and having a USB flash key handy to use as the installer media.
Did this work for you? Do you know of another way to create an ISO file of macOS Big Sur installers, MacOS Catalina installers, or make an ISO of an macOS Mojave installer? Let us know your experiences in the comments below.
Is this going to get updated?
Mistakes the Guide missed.
First I’m running into the:
sudo /Applications/Install\ macOS\ Big\## Sur.app##/Contents/Resources/createinstallmedia –volume /Volumes/MacBigSur –nointeraction
Issue –
Now im running into the:
/Volumes/MacBigSur is not large enough for install media. An additional 413.8 MB is needed.
issue – ~
Since when does one read the comments before they guide?
The guide is fine, your syntax is not.
Command line necessitates precise syntax, or things will fail.
It also looks like your volume, named MacBigSur, is not big enough to create an ISO file for Big Sur with. Try using a larger USB key or flash drive.
Hello,
Point 6 needs correction (adding .app to installer’s name):
sudo /Applications/Install\ macOS\ Big\ Sur.app/Contents/Resources/createinstallmedia –volume /Volumes/MacBigSur –nointeraction
Note parameters use double — , not single –
Having an issue getting my installer to work in that after the installer loads up and I select disk to install to I get an error that “Installer damaged and can’t continue. Please redownload.”
Think its because I created a “SharedSupport” folder inside the installosx.app app and copied the SharedSupport.esd file into there or else the ‘createinstallmedia’ command wouldn’t work.
Any ideas please?
Thanks
Here is how I did it, all Terminal except the App Store download.
1: First download macOS Big Sur installer from App Store or if elsewhere and put it in /Applications folder
2: Make the tmp volume
sudo hdiutil create -o /tmp/BigSur -size 17600m -volname BigSur -layout SPUD -fs HFS+J3: Mounted the disk image
sudo hdiutil attach /tmp/BigSur.dmg -noverify -mountpoint /Volumes/BigSur4: Used the disk image as destination for creating installer using Mac App Store download
sudo /Applications/Install\ macOS\ Big\ Sur.app/Contents/Resources/createinstallmedia --volume /Volumes/BigSur --nointeraction5: Convert the tmp image to cdr file
hdiutil convert /tmp/BigSur.dmg -format UDTO -o ~/Downloads/BigSur.cdr6: Convert the CDR to ISO by renaming it
mv -v ~/Downloads/BigSur.cdr ~/Downloads/BigSur.iso7: Do with the ISO whatever you want, for me it is for creating virtual machine
8: Eject the original mounted volume or reboot Mac and the volume will eject
hdiutil eject -force /Volumes/Install\ macOS\ Big\ Sur9: Reboot will clear this automatically or you delete the tmp file manually
sudo rm -rf /tmp/BigSur.dmgI did this for a virtual machine, but for other Macs I make a boot flash drive instead.
Here are the things that worked for me:
Command not found – only works if the installer image is mounted which you can check in finder and if not there, double click on the ‘Install MacOS Bug Sur’ in the Applications folder.
The Volume could not be found – make sure there are two minus symbols in front of each argument in step 6 as follows:
sudo /Applications/Install\ macOS\ Big\ Sur.app/Contents/Resources/createinstallmedia –volume /Volumes/MacBigSur –-nointeraction
One step missing between 5 and 6, especially if you are trying to do this on Catalina:
After step 5, your terminal should display something like this:
sh-3.2# hdiutil attach /tmp/MacBigSur.dmg -noverify -mountpoint /Volumes/MacBigSur
/dev/disk2 Apple_partition_scheme
/dev/disk2s1 Apple_partition_map
/dev/disk2s2 Apple_HFS /Volumes/MacBigSur
At this point, do the following
diskutil eraseDisk JHFS+ MacBigSur disk2
This is the correct sequence:
hdiutil create -o /tmp/MacBigSur -size 13500m -volname MacBigSur -layout SPUD -fs HFS+Jhdiutil attach /tmp/MacBigSur.dmg -noverify -mountpoint /Volumes/MacBigSur
sudo /Applications/Install\ macOS\ Big\ Sur.app/Contents/Resources/createinstallmedia --volume /Volumes/MacBigSur --nointeraction
sudo hdiutil detach /Volumes/Install\ macOS\ Big\ Sur/ -force
hdiutil convert /tmp/MacBigSur.dmg -format UDTO -o ~/Desktop/MacBigSur.cdr
mv ~/Desktop/MacBigSur.cdr ~/Desktop/BigSur.iso
So hat es bei mir auch funktioniert. Danke :)
Thank you..
amazing how comments 3 yrs old are more up to date that the moderated guide.
In section (6), I get the command not found after execution. I don’t why. I don’t see anything that is incorrect or missing.
I get the following error on step #6 – Command not found
I don’t know why!
I get the following error on step #6 – Command not found
sudo: /Applications/Install macOS Big Sur/Contents/Resources/createinstallmedia: command not found
I don’t know why!
The Big Sur installer may have “.app” appended to it’s name.
Try this:
sudo /Applications/Install\ macOS\ Big\ Sur.app/Contents/Resources/createinstallmedia –volume /Volumes/MacBigSur –nointeraction
you need write –volume (not -volume)
need two – (not only one)
You can’t. the installer is static, once you create one, it cant update itself. :-p
Often times the installer itself isn’t up-to date…There are almost always updates after a fresh install, even when the installer was freshly created.
OK, but isn’t this just the same as your previous explainer? And as with that, you can abbreviate the process by creating a CDR image to begin with, instead of converting a dmg into a CDR (see my comment in the linked article).
How can we create a USB installer that always contains the latest patches without downloading the 12GB file again and again?
You can’t. the installer is static, once you create one, it cant update itself. :-p
Often times the installer itself isn’t up-to date…There are almost always updates after a fresh install, even when the installer was freshly created.
In section (6) terminal line you left “Beta” within the line.
Its simpler to create and mount a disc image then use createinstallmedia the same way you would to create a USB installer pointing the installer at the mounted disk image
Having an issue getting my installer to work in that after the installer loads up and I select disk to install to I get an error that “Installer damaged and can’t continue. Please redownload.”
Think its because I created a “SharedSupport” folder inside the installosx.app app and copied the SharedSupport.esd file into there or else the ‘createinstallmedia’ command wouldn’t work.
Any ideas please?
Thanks