Apple released OS X Mountain Lion yesterday exclusively as a digital download via Mac App Store for $19.99, or free if you own a qualifying new Mac computer. While Apple has decided not to sell the update on optical media or USB sticks, you can always keep a physical copy of your Mac App Store download in the form of a bootable OS X Mountain Lion install DVD or a USB key. This is more useful if you ever want to do a clean install of the operating system.
Below are the step-by-step instructions on how to create a bootable OS X Mountain Lion install DVD or a USB drive:
Download OS X Mountain Lion from the Mac App Store, but don’t install it yet.
Find the installer in your Applications folder and right-click on it then select “Show Package Contents.” Browse to Contents > SharedSupport and look for the file called “InstallESD.dmg”
Now open up Disk Utility from your Applications > Utilities folder and drag the DMG file into the sidebar on the left.
If you’re burning to DVD: insert your disk, select the DMG file in the sidebar, and hit “Burn“. Skip to step 6.
If you’re creating a USB drive, you’ll need to first format the drive properly:
- Insert the USB disk and select it in the sidebar in Disk Utility. Select the Partition tab, select “1 Partition” from the dropdown menu and choose “Mac OS Extended (Journaled)” for the format type.
- Click the Options button and choose “GUID Partition Table“. This will make the drive bootable and formatted correctly for the Mac. Hit Apply to format.
- Now click the Restore tab and choose the DMG file as your source and the USB drive as the destination. Hit the Apply button to begin the process.
Finally, to boot from your install DVD/USB key and install OS X Mountain Lion, restart your Mac and hold the Option key down when you hear the startup chime.
That’s it. Enjoy!