A (relatively) simple guide to create a Bootable MacOS installer USB on Windows

Create a MacOS installer USB (on Windows).md

Create a Bootable MacOS installer USB on Windows

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.

A few comments have mentioned easier ways to make a bootable MacOS USB drive:

this blog post uses UltraDMG and has worked for some (and is easier)

if using this archive.org page people have mentioned after Restore with Disk Image in Step 3, the USB is ready to boot and you can skip straight to Step 4.

Will update this gist soon™

1. Obtaining the image

• 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.

• Alternatively, go to this archive.org page for all MacOS images and download your version DMG.

2. Preparing the files

• 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

3. Creating the install media

• 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.dmg and 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.

4. Booting and Installing

• 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!

5. Uninstalling and Cleaning (Optional)

• TODO

All credit to: https://www.youtube.com/watch?v=_g8naTAC9jA

hi. the dmgs in the archive.org link work perfectly on their own. the files seemed ready to me so i just formatted then restored the download as is.

for reference i chose monterey and plugged it into a macbook air 2017. good luck

Thank you, so much for sharing!! I having a hard time figuring out what to do with this laptop since it couldn't seem to connect to Apple's servers.

I had some trouble finding the Packages folder I was supposed to back up (I should have checked the "repacking" part sooner); however, this worked perfectly for me for installing Lion (macOS X 10.7)!

Hi. I can't still find the Packages folder. How did you find that or what was the workaround?

Thanks!

I can't still find the Packages folder. How did you find that or what was the workaround?

I found it in USB-Disk\OS X Base System\System\Installation\ . I only thought to look there because that's where you are supposed to put the Packages folder on the "edited" DMG.

I can't still find the Packages folder. How did you find that or what was the workaround?

I found it in USB-Disk\OS X Base System\System\Installation\ . I only thought to look there because that's where you are supposed to put the Packages folder on the "edited" DMG.

Thank you, it helped me find it, but it still doesn't work.
When I boot, I am welcomed by the 🛇 icon without any error code or message.

I can guess it's because the hardware is not compatible with the OS I'm trying to install. I was trying to find a workaround, since I can't install OCLP on that machine and can't upgrade past El Capitan.

Will make a new post asking for help I guess.

can't install OCLP on that machine and can't upgrade past El Capitan.

Do you know which OS came on the computer? I would start the process there and update to the version you want.
Unless ... Apple is very controlling. It might be easier to put the "correct" OS on as bases system and then see if you can run others as a VM.