How to Get macOS Big Sur as a DMG File
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.
- 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)
- When the download has finished, open the Terminal application
- From the command line, create the disk image DMG file destination and temporary volume by issuing the following command:
- Mount the disk image with the following command:
- Next, use createinstallmedia utility to copy the installer files to the disk image DMG file you just created:
- Unmount the newly created volume with the following command:
- Now, move the macOS Big Sur DMG file to the user desktop for easy access:
hdiutil create -o /tmp/MacOSBigSur -size 16500m -volname MacOSBigSur -layout SPUD -fs HFS+J
hdiutil attach /tmp/MacOSBigSur.dmg -noverify -mountpoint /Volumes/MacOSBigSur
sudo /Applications/Install\ macOS\ Big\ Sur.app/Contents/Resources/createinstallmedia --volume /Volumes/MacOSBigSur --nointeraction
hdiutil detach /Volumes/MacOSBigSur/
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.