Create the Mountain Lion install drive

There are a couple ways you can create a bootable install drive: using OS X’s own Disk Utility or using the third-party utility Carbon Copy Cloner. The latter is easier, but the former doesn’t require you to download third-party software. A third option is Lion DiskMaker, an update to that utility that also supported OS X Lion.

Note that whichever method you use, you need a hard drive or thumb drive (USB stick) at least 5GB in size (an 8GB flash drive works well), and it must be formatted with a GUID Partition Table.

 

Using Disk Utility You’ll find this utility in your Utilities folder (in /Applications/Utilities). Here are the steps for using it to create your installer drive:


Right-click (or Control+click) on the Mountain Lion installer to view its contents.

  1. Once you’ve purchased Mountain Lion, find the installer on your Mac. It’s called Install OS X Mountain Lion.app and it should have been downloaded to your main Applications folder (/Applications).
  2. Right-click (or Control+click) the installer, and choose Show Package Contents from the resulting contextual menu.
  3. In the folder that appears, open Contents, then open Shared Support; you’ll see a disk image file called InstallESD.dmg.
  4. Launch Disk Utility.
  5. Drag the InstallESD.dmg disk image into the bottom (empty area) of Disk Utility’s sidebar (on the left).
  6. In Disk Utility, select InstallESD.dmg in the sidebar, and then click the Open button in the toolbar to mount the disk image’s volume in the Finder. The mounted volume is called Mac OS X Install ESD, and it also appears below InstallESD.dmg in Disk Utility.
  7. Select Mac OS X Install ESD in Disk Utility’s sidebar, then click the Restore button in the main part of the window.
  8. Drag the Mac OS X Install ESD icon into the Source field on the right (if it isn’t already there).
  9. Connect to your Mac the properly formatted hard drive or flash drive you want to use for your bootable Mountain Lion installer.
  10. In Disk Utility, find this destination drive in the left-hand sidebar and then drag it into the Destination field on the right. (If the destination drive has multiple partitions, just drag the partition you want to use as your bootable installer volume.) Warning: The next step will erase the destination drive or partition, so make sure it doesn’t contain any valuable data.
  11. Click Restore, and then Erase in the dialog box that appears; if prompted, enter an admin-level username and password.

The restore procedure will take roughly five to ten minutes, depending on your Mac and the speed of your drive(s).

(If you ever created a bootable Lion-install drive, you may have performed the above procedurewithout mounting the InstallESD disk image. As of version 10.7.4 of the Lion installer, and continuing with the Mountain Lion installer, you must use the mounted Mac OS X Install ESD volume or you’ll get an error at the end of the restore procedure, and the newly created bootable drive may not function properly.)

 


You can use Disk Utility’s Restore screen to create a bootable flash drive or hard drive.

 

Using Carbon Copy Cloner Version 3.5 or later of this excellent clone-backup utility includes a special feature for creating a bootable install drive. (Carbon Copy Cloner is free to try; you can purchase a license for $40.) Once you’ve downloaded it from the developer’s website—or, if you already had it, once you’ve checked to make sure you’ve got the latest version—follow these steps:

  1. Find the Mountain Lion installer on your Mac. It’s called Install OS X Mountain Lion.app and it should have been downloaded to your main Applications folder (/Applications). Note that Carbon Copy Cloner requires that the installer be located in the Applications folder on your boot drive.
  2. Connect to your Mac the properly formatted hard drive or flash drive you want to use for your bootable Mountain Lion installer.
  3. Launch Carbon Copy Cloner.
  4. In the Source pop-up menu (labeled Select A Source), choose Create a Mountain Lion Installer. (This mounts the InstallESD.dmg disk image, mentioned above, and selects it as the source volume.)
  5. In the Destination pop-up menu (labeled Select A Destination), choose the drive you’re using for your bootable installer.
  6. In the Handling Of Data Already On The Destination pop-up menu, choose Delete Anything That Doesn’t Exist On The Source. Warning: The next step will effectively erase the destination drive or partition, so make sure it doesn’t contain any valuable data.
  7. Click Clone, click Continue in the warning dialog that appears, and, when prompted, provide an administrator username and password.


Carbon Copy Cloner can create a bootable Mountain Lion installer in a few easy steps.

 

As with using Disk Utility, the process takes roughly five to ten minutes. One difference here: Whereas using Disk Utility names your bootable drive Mac OS X Install ESD, using Carbon Copy Cloner keeps the drive’s original name.

Booting from the installer drive

You can now boot any Mountain Lion-compatible Mac from this drive: Just connect the drive to your Mac and either (if your Mac is already booted into OS X) choose your install drive in the Startup Disk pane of System Preferences or (if your Mac is currently shut down) hold down the Option key at startup and choose the install drive when OS X’s Startup Manager appears.

When booted from your install drive, you can, of course, install the OS, but you can also use any of the Mountain Lion installer’s special recovery and restore features—in fact, when you boot from this drive, you’ll see the same OS X Utilities screen you get when you boot into restore mode. However, unlike restore mode, your bootable installer includes the entire installer.