Drag the formatted partition to the “Destination” section, then click on “Restore”.

Drag the previously mounted “Mac OS X Install ESD” image into the “Source” section.

Now select the formatted USB drive from the left side and click on the “Restore” tab.

Select the USB drive from the left menu and click on “Erase” tab, choose “Mac OS X Extended (Journaled)” as the format, then click on the “Erase” button in the corner.

Launch Disk utility and connect a USB drive to the Mac.

Make the OS X Mountain Lion Install Drive

Double-click on InstallESD.dmg to mount it on the desktop.Open the “Contents” directory and then open “SharedSupport”, looking for a file named “InstallESD.dmg”.Go to the /Applications/ directory and right-click on “Install Mac OS X Mountain Lion.app” selecting “Show Package Contents”.Download OS X 10.8 Mountain Lion from the App Store.

Download OS X Mountain Lion and Extract the DMG File If you already have the Mac OS X Mountain Lion install DMG extracted, skip this first set of steps and jump directly to making the bootable drive below. We’ll walk through the process here, but don’t forget to check OS X 10.8 system requirements for the destination Mac before beginning. Select Recovery HD from the Startup Manager.įor detailed information on this update, please visit: About OS X Recovery Disk Assistant.By creating a bootable install drive, you can perform clean OS X 10.8 installs, install it on separate partitions, and install OS X Mountain Lion on Macs that don’t have internet connections. To access OS X Recovery, reboot the computer while holding the Option key. When the OS X Recovery Disk Assistant completes, the new partition will not be visible in the Finder or Disk Utility. Insert an external drive, launch the OS X Recovery Disk Assistant, select the drive where you would like to install, and follow the on screen instructions. To create an external OS X Recovery, download the OS X Recovery Disk Assistant application. Note: In order to create an external OS X Recovery using the OS X Recovery Assistant, the Mac must have an existing Recovery HD. The OS X Recovery Disk Assistant lets you create OS X Recovery on an external drive that has all of the same capabilities as the built-in OS X Recovery: reinstall Lion or Mountain Lion, repair the disk using Disk Utility, restore from a Time Machine backup, or browse the web with Safari. Built right into OS X, OS X Recovery lets you repair disks or reinstall OS X without the need for a physical disc.

Mountain lion disk