Note! Before proceeding, please make sure that you have a USB flash drive at least 8GB in size. All data will be destroyed on this drive, so please back up your files.
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Go to this apple.com support article (10.7 Lion - 10.12 Sierra) and scroll down to "Use a web browser for older versions" Right click your desired OS and click "Save link as". Save the DMG to a folder.
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Alternatively, go to this archive.org page for all MacOS images and download your version DMG.
- Using a program such as 7-Zip, open InstallMacOSX.dmg
- If you don't already have 7-Zip, download it from the link above and run the installer.
- Navigate to
InstallMacOSX.dmg\Install OS X\InstallMacOSX.pkg\InstallMacOSX.pkg\InstallESD.dmg\OS X Install ESD\ - Extract the BaseSystem.dmg, BaseSystem.chunklist and Packages folder to a folder of your choice
- Now navigate to
InstallMacOSX.dmg\Install OS X\InstallMacOSX.pkg\InstallMacOSX.pkg\InstallESD.dmg\OS X Install ESD\BaseSystem.dmg\OS X Base System\Install OS X El Capitan.app\Contents\Resources\and extract InstallAssistant.icns - Quit the archiver. We won't be using it anymore.
- In your File Manager (Explorer), rename InstallAssistant.icns to --->
.VolumeIcon.icns
- Download TransMac (Paid software with Trial) and run the installer.
- Insert your desired USB flash drive (8GB+) and run TransMac as Administrator (this will give it the neccessary rights to write to the USB drive.
- Wait 10s! and hit "Run"
- Select your desired USB flash drive and right-click it. Select Format Disk for Mac
- Once finished, right click again, and select Restore with Disk Image
- Select your previously extracted
BaseSystem.dmgand hit OK - Select Enlarge Volume to Drive Size and press OK
- Wait a bit for the files to copy over.
- Select your USB drive in the sidebar of TransMac. There should be a folder called "OS X Base System". Click on the folder.
- The right window pane should show a folder structure
- Go back to your File Manager, and locate and select BaseSystem.dmg, BaseSystem.chunklist and .VolumeIcon.icns
- Drag all 3 files to into the right pane of TransMac. They should begin to copy over.
- Still in TransMac, navigate to
USB-Disk\OS X Base System\System\Installation\ - Delete the "Packages" File
- Replace this with the "Packages" Folder that we extracted earlier.
- Wait for the folder to copy over.
- That's it! Eject the USB flash drive and unplug it from your computer.
- Go over to your Mac. Make sure it is shut down.
- Plug in the USB flash drive we just created.
- While holding the Option (Alt) key, power on your Mac. Keep holding the Option key.
- When you see a menu with your USB flash drive on it, release the key.
- Select OS X Base System and hit Enter
- Follow the installation prompts!
- TODO
All credit to: https://www.youtube.com/watch?v=_g8naTAC9jA
Hey, did you get around to testing UltraDMG yet?
Just to share — TransMac is paid and honestly pretty expensive (US $59 for a single user license). UltraDMG is way cheaper and does the same thing when it comes to creating macOS bootable USBs.
And from my own experience, on Windows there really isn’t any free tool that can properly make a Mac bootable installer, so it might be worth replacing TransMac to UltraDMG in your gist. That way people don’t assume they need to spend that much just to get it working.
UltraDMG works great on my Windows 11 laptop: