How to Get macOS Big Sur as a DMG File

May 3, 2021 - 11 Comments

macOS Big Sur DMG

Some Mac users may be interested in obtaining macOS Big Sur as a DMG file, so that they can use the disk image with a virtual machine, to create bootable media, for archival purposes, for cloning, or any other reason. It turns out that macOS Big Sur is available to download as an installer application, and from that you can build a macOS Big Sur DMG file, and that’s what we’ll show you how to do.


For what it’s worth, if you’re looking to create boot media, it’s probably better to simply make a macOS Big Sur bootable install USB drive using the more traditional approach. Nonetheless, if you’re wanting a macOS Big Sur DMG, here’s how you can get one.

Downloading macOS Big Sur as a DMG File

We will walk through the process of getting a macOS Big Sur DMG file by building one from the downloaded installer media. We’re focusing on macOS Big Sur but this approach works with other macOS releases too.

  1. Get macOS Big Sur from the Mac App Store (you can download other macOS installers from here if needed. If you’re already on macOS Big Sur you can re-download the installer with these instructions)
  2. When the download has finished, open the Terminal application
  3. From the command line, create the disk image DMG file destination and temporary volume by issuing the following command:
  4. hdiutil create -o /tmp/MacOSBigSur -size 16500m -volname MacOSBigSur -layout SPUD -fs HFS+J

  5. Mount the disk image with the following command:
  6. hdiutil attach /tmp/MacOSBigSur.dmg -noverify -mountpoint /Volumes/MacOSBigSur

  7. Next, use createinstallmedia utility to copy the installer files to the disk image DMG file you just created:
  8. sudo /Applications/Install\ macOS\ Big\ Sur.app/Contents/Resources/createinstallmedia --volume /Volumes/MacOSBigSur --nointeraction

  9. Unmount the newly created volume with the following command:
  10. hdiutil detach /Volumes/MacOSBigSur/

  11. Now, move the macOS Big Sur DMG file to the user desktop for easy access:
  12. mv /tmp/MacOSBigSur.dmg ~/Desktop/

At this point you’ll have the MacOSBigSur.dmg disk image file on the current users desktop, and you can do with it what you want, whether that’s to import it into a VM, creating a boot utility, or whatever else you’re looking to do.

The steps outlined above are similar to creating a macOS Big Sur ISO file, except you don’t convert the DMG file to a CDR / ISO.

If you were hoping for a direct download link to SharedSupport.dmg / InstallESD.dmg for macOS Big Sur, you’ll find that Apple does not supply one, thus the need to use a method like that detailed above. You may find dubious resources online pointing to third party download links, but those are not recommended to use for a variety of security reasons.

Did you make a macOS Big Sur DMG? Know of another approach to download an authentic macOS Big Sur DMG file? Let us know your experiences and tips in the comments.

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Posted by: Paul Horowitz in Mac OS, Tips & Tricks

11 Comments

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  1. Aakash says:

    I got this for big sur from Mojave
    /Applications/Install macOS Big Sur.app does not appear to be a valid OS installer application.

    but I created a dmg for Catalina using the same process.

    any reason why this big sure is not a valid installer? I see the package contents of it has everything.

  2. Mike B. says:

    Syntax error for instruction #5. Should read:”Big\Sur.app”

  3. Garry says:

    using the above method to download Big Sur can it be installed on an older Mac mini 2011

    If not

    can it run as a virtual machine and where do I find the information to do this

  4. Al Maloney says:

    I have a problem – got msg

    sudo: /Applications/Install macOS Big Sur/Contents/Resources/createinstallmedia: command not found

    What do I do?

    • Paul says:

      That is often because the macOS installer is not located in the Applications folder

      In this case it looks like your file path is incomplete though, it should be:

      /Applications/Install macOS Big Sur.app/Contents/Resources/createinstallmedia

  5. Trent Turner says:

    Can I do this for older versions of OSX?
    I have a game that needs an older version, e. g.10.6!

  6. David says:

    The sudo command “/Applications/Install\ macOS\ Big\ Sur/Contents/Resources/createinstallmedia…” comes up “Command not found”.

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