Knowledgebase

The Mountain Lion install image that we need to create either the bootable DVD or the bootable USB flash drive is contained within the Install OS X Mountain Lion file we downloaded from the Mac App Store.

Because the image file is contained within the downloaded file, we need to copy it to the Desktop to make creating the bootable image as easy as possible.

1. Open a Finder window, and navigate to your Applications folder (/Applications).


2. Scroll through the list of files and locate the one named Install OS X Mountain Lion.


3. Right-click the Install OS X Mountain Lion file and select "Show Package Contents" from the pop-up menu.


4. You will see a folder named Contents in the Finder window.


5. Open the Contents folder, and then open the SharedSupport folder.


6. You should see a file named InstallESD.dmg.


7. Right-click the InstallESD.dmg file and select "Copy InstallESD.dmg" from the pop-up menu.


8. Close the Finder window and return to the Desktop.


9. Right-click on an empty area of the Desktop and select "Paste Item" from the pop-up menu.

Pasting the item to the Desktop can take a bit of time, so be patient.

When the process is finished, you'll have a copy of the InstallESD.dmg file that we need to create bootable copies.

Next.

With Mountain Lion's InstallESD.dmg file copied to the Desktop (see previous page), we're ready to burn a bootable DVD of the installer. If you would rather create a bootable copy on a USB flash drive, you can skip this page and go on to the next page.

1. Insert a blank DVD into your Mac's optical drive.
2. If a notice asks you what to do with the blank DVD, click the Ignore button. If your Mac is set up to automatically launch a DVD-related application when you insert a DVD, quit that application.


3. Launch Disk Utility, located at /Applications/Utilities.


4. Click the Burn icon, located in the top right corner of the Disk Utility window.


5. Select the InstallESD.dmg file you copied to the Desktop in an earlier step.


6. Click the Burn button.


7. Place a blank DVD into your Mac's optical drive and click the Burn button again.


8. A bootable DVD containing OS X Mountain Lion will be created.


9. When the burn process is complete, eject the DVD, add a label, and store the DVD in a safe location.

Creating a bootable copy of Mountain Lion on a USB flash drive isn't difficult; all you need is the InstallESD.dmg file that you copied to your Desktop on page 2 of this guide (and a flash drive, of course).

Erase and Format the USB Flash Drive

1. Insert the USB flash drive into your Mac's USB port.


2. Launch Disk Utility, located at /Applications/Utilities.


3. In the Disk Utility window that opens, scroll through the list of devices in the left-hand pane and select your USB flash device. It may be listed with multiple volume names. Do not select a volume name; instead, select the top-level name, which is usually the name of the device, such as 16GB SanDisk Ultra.


4. Click the Partition tab.


5. From the Partition Layout drop-down menu, select 1 Partition.


6. Click the Options button.


7. Make sure that GUID Partition Table is selected from the list of available partition schemes. Click OK. Warning: All data on the USB flash drive will be deleted.


8. Click the Apply button.


9. Disk Utility will ask you to confirm that you wish to partition the USB device. Click the Partition button.

The USB device will be erased and partitioned. When that process is complete, the flash drive is now ready for use as a bootable device for OS X Mountain Lion.

Copy the InstallESD.dmg File to the Flash Drive

1. Make sure the USB flash device is selected in the device list in Disk Utility. Remember: do not select the volume name; select the device name.


2. Click the Restore tab.


3. Drag the InstallESD.dmg item from the device list (it will be near the bottom of Disk Utility's device list; you may need to scroll down to find it) to the Source field.


4. Drag the USB flash device's volume name from the device list to the Destination field.


5. Some versions of Disk Utility may include a box labeled Erase Destination; if yours does, make sure the box is checked.


6. Click Restore.


7. Disk Utility will ask if you really wish to perform a restore, which erases all information on the destination drive. Click Erase.


8. If Disk Utility asks for your administrator password, provide the information and click OK.

Disk Utility will copy the InstallESD.dmg data to the USB flash device. When the copying is complete, you will have a bootable copy of OS X Mountain Lion ready for use.

Credits to http://macs.about.com/od/macoperatingsystems/ss/Create-Bootable-Copies-Of-The-Os-X-Mountain-Lion-Installer_2.htm for a beautifull guide.