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How To: Create A Bootable OS X Mountain Lion Install DVD Or USB Key [Guide]

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:

Step 1:

Download OS X Mountain Lion from the Mac App Store, but don’t install it yet.

Step 2:

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

Step 3:

Now open up Disk Utility from your Applications > Utilities folder and drag the DMG file into the sidebar on the left.

Step 4:

If you’re burning to DVD: insert your disk, select the DMG file in the sidebar, and hit “Burn“. Skip to step 6.

Step 5:

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.

Step 6:

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!

“Technology runs through my veins...” | Follow me: @DrUsmanQ usman@iPhoneinCanada.ca

  • http://twitter.com/adamjefferson Adam Jefferson

    A must for anyone with multiple Macs!

  • Benoit Turcotte

    Aren’t we a little off topic here ?

  • Flocho

    Would this process allow one to install Mountain Lion on an iMac running Leopard? Or would you still have to upgrade to Snow Leopard first (install app store icon) then d/l Mountain Lion?

  • Stir_Fry

    I tried this last night about 6 times to do this. Woudn’t work for me. I was never sucessful in doing a clean install of 10.8.0. It kept bringing up the error “Can not download required components. File is corrupted or has been tampered with.” Sometimes, it would boot off my flash drive and then just shut down. The only way I was able to install ML on my 13″ 2011 MBP is to install Lion then install ML over the top. I fixed my permissions and formatted the drive many times. I have an Intel SSD Cherryville 120 GB 6GB/S and a 500 GB WD Scorpio Blue in the optical bay. I also have 8GB of OWC RAM

  • Carolynn

    Any recommendations on how to do this if you already installed Mountain Lion? I’d love to have a back-up.

  • Usman

    Download from the Mac App Store again and before hitting the install button, copy the OS X ML installer from Applications folder and extract “InstallESD.dmg”.

  • Carolynn

    Thank you so much! {grateful newbie}

  • asdf

    everything went well until the last step where I clicked “restore”. it says’ “restore failure” could not restore – Resource busy

  • Ed

    How about if my MacBook Pro come with ML and I could not re-download the ML from the App store? Any alternatives?