How To Make A Bootable Disk Or USB Drive Of OS X Mountain Lion


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Apple only sells OS X Mountain Lion as a digital download in the Mac App Store. The installer weighs in at a hefty 4.05GB, but the good news is that you can install your copy of Mountain Lion on all of your Macs for no extra charge. Technically, the Mountain Lion installer can be used on an infinite number of Macs once you have it; you just need to make a bootable disk or drive.

See, the Mountain Lion installer is set to self-destruct once it’s used. When your Mac reboots running Mountain Lion, the installer will be gone and you’ll have to re-download it if you want to use it again. Another reason to create a bootable copy of Mountain Lion is if you want to do a clean install. Apple’s installer will keep your files and personal setup intact while installing Mountain Lion, but a bootable disk will allow you to erase your Mac and start completely anew.

The good news is that creating a bootable disk or USB drive of Mountain Lion is pretty simple.

Before you begin: You’ll need to make a backup of your Mountain Lion installer before trying to create a bootable copy. Use the copy you make to create a bootable disk or follow this process before you install Mountain Lion on the Mac you’re currently using.

What You’ll Need:

  • blank 8GB+ USB/external drive or blank 4.7GB DVD disk
  • $20 Mountain Lion installer app from the Mac App Store

The Easy Way

As we already told you, the Lion Disk Maker app has been updated with Mountain Lion support. This simple, free app walks you through creating a bootable disk/drive of Mountain Lion.

The whole process should take no more than an hour on even the slowest of Macs. Obviously, writing to a disk is going to take longer than creating a bootable flash drive or SD card.

The DIY Way

If you’d rather make a bootable copy yourself, then Apple’s Disk Utility is about to be your best friend.

In Finder, right click on the Mountain Lion installer and click “Show Package Contents.” Navigate to Contents > SharedSupport. You’ll see a disk image called “InstallESD.dmg.” This is your ticket to creating a bootable copy of Mountain Lion.

Open the Disk Utility app in the Utilities folder under Applications. Drag the “InstallESD.dmg” into the white box on the left side of Disk Utility, and the disk image will be added. Now insert your disk or USB drive.

If you’re using a flash drive, make sure it’s partitioned as “Mac OS Extended (Journaled)” under the “Partition” section in Disk Utility. Make sure the drive is empty and that there is only one partition.

To start making your bootable copy of Mountain Lion, drag the drive you just added to Disk Utility from the source list in the top left of the app’s white space to the “Destination” path of the “InstallESD.dmg” image. Hit “Restore” and let Disk Utility work its magic.

For creating a bootable disk with your Mac’s SuperDrive, the process is even simpler. With the “InstallESD.dmg” selected in Disk Utility, click “Burn” in the top toolbar. Select the “InstallESD.dmg” image as the source for burning your disk.

Once Disk Utility is done, you’re good to go.

A Clean Install

Now that you have a bootable copy of Mountain Lion, this drive/disk acts as a full-fledged setup tool for upgrading other Macs to the new OS. For a clean install of Mountain Lion on any compatible Mac, follow these steps:

  1. Insert your bootable disk or drive.
  2. Restart your Mac while holding down the option key. This will bring up the installer.
  3. Inside the Mountain Lion installation tool, you can open Disk Utility and erase your Mac’s hard drive. From the erase tab, choose “Mac OS Extended (Journaled)” and wipe your drive. (Make sure you have a backup first, just in case.)
  4. Once your Mac’s hard drive is erased, quit Disk Utility and go back into the Mountain Lion installer. Choose your Mac’s hard drive and begin installing Mountain Lion.

By following those steps, your Mac will be restored to Apple’s stock setup and all of your personal files will be gone.

If you’d rather install Mountain Lion without a bootable copy and keep your setup the way it is, refer to our general tutorial. For more on Mountain Lion, be sure to read the official Cult of Mac review.

  • AndyAndreas

    Can I create a new partition to install Mountain Lion and keep intact my Lion 10.7.4?

    What if I already have another partition (with Ubuntu)? Do I have to delete it as well to make a clean install or can I keep it?

    Anyway, you are the best :) Thank you for your guide.

  • darknightrising

    Neither way will work for me. Tried using the Lion Diskmaker first and it just keeps coming up with the error “The disk could not be created because of an error: An error occurred: -43. File ASObjC Runner wasn’t found.”

    When trying to use OS X’s Disk Utility the DIY way I am just getting the error “Restore Failure Could not restore – resource busy”

  • Daniel Brazil

    It needs an Double Layer DVD =D

  • boobert

    if your using a thumb drive and you repartitioned it and didn’t name it like me lol (mine was listed under my 8gb thumb drive as Untitled 1)you have to drag that one to the destination spot and the InstallESD.dmg to the source and it should work.:)

  • EvilDevilEvil

    I have recently bought a MacBook Air 13″ base model. How can I create a recovery disk? I mean shall I have to buy Mtn Lion again? It’s already on my Mac. Or is there a tool that can create a recovery image or disk to a pen drive just from my current Mac Installation?

    • Donald Kepler

      Try Stellar Clone Drive tool for cloning entire Mac HDD including Recovery HD. This tool provides an option of Restoring data from the created Image. Good Luck !

  • Almost_Correct

    Um… You left out a major step before you can drag the image name to the source field: Click the memory stick name, then click the ‘Restore’ tab at the top of the right hand panel.

  • shahanmol1

    Neither way will work for me.

    Tried using the Lion Diskmaker first and it just keeps coming up with the error “The disk could not be created because of an error: An error occurred: -43. File ASObjC Runner wasn’t found.”

    When trying to use OS X’s Disk Utility the DIY way I am just getting the error “Restore Failure Could not restore – resource busy”

    I really need help with this asap.
    Thank You

  • Loneranger123

    The writer of this article has shown complete incompetence in writing these instruction where important steps are missed out.

    I blame the idiot who interviewed this chap for his job.

  • madelefant

    Why would you need to create a bootable install disk using lion disk maker if you have it already installed and you can just use disk image to make an image of the start-up drive? How do you make a backup of your startup drive that restores both the system and the files if you have a crash? I cant imagine wanting to do it any other way.