Create Bootable USB/CD for OS X Mountain Lion


I bought my first MacBook Pro last Saturday and it was great experience. Since the computer is not pre-installed with any version of OS X, I asked the salesman to install OS X Mountain Lion for me and she was very kind to help me out. Later when I came back home, one of my roommates told me that he wanted to update this Macbook Air from OS X 10.6.8 to the latest 10.8.2. Now I am wondering if there is any way to make the Mountain Lion system to be a .dmg file so I can do a little favor for his Mac.


OS X Mountain Lion was released on July 25, 2012 for purchase and download through Apple's Mac App Store, as part of a switch to releasing OS X versions online and every year. Like OS X 10.7 Lion, you can create your own bootable USB key or CD installer to use as a recovery disk or to install Mountain Lion on multiple Macs. This saves huge amount of time as you don’t have to download the 4GB file multiple times.


Note in advance: it is suggested that you learn the system requirements for OS X Mountain Lion from this Apple knowledge base article. For some Mountain Lion features have additional requirements.


Step by Step Guide to Create OS X Mountain Lion USB Key

  • If needed, re-download the installation package of OS X Mountain Lion from App Store, using the same Apple ID.
  • Go to the /Applications/ directory and right-click on “Install Mac OS X Mountain” selecting “Show Package Contents”.
  • Open the “Contents” directory and then open “SharedSupport”, looking for a file named “InstallESD.dmg”, then double-click on this file to mount it on the desktop.
  • Launch Disk utility and connect your handy USB key to your Mac machine.
  • Select the flash drive from the left menu and click on “Erase” tab, choose “Mac OS X Extended” as the format, then click on the “Erase” button in the corner.
  • Now select the formatted USB drive from the left side and click on the “Restore” tab, drag the previously mounted “Mac OS X Install ESD” image into the “Source” section.
  • Drag the formatted partition to the “Destination” section, and then click on “Restore”.
  • Finally confirm that the USB drive will lose its data and enter the Admin password if asked.


Here is a simple steps to create bootable USB key for OS X Mountain Lion. If all went well, you have now an installation USB key and from which you can directly start the installation of OS X 10.8. Also, it is the same thing if you need it to be on your CD or DVD.


After booting from the installation USB or CD, you can either restore from a Time Machine backup or re-install OS X.