In Disk Utility, do the following 4 steps carefully: You can do it quickly by searching via Spotlight. Plug in the flash drive into your Mac and launch the Disk Utility application. Navigate to Contents > SharedSupport, then look for the filename “InstallESD.dmg”ĭouble-click InstallESD.dmg to open/mount it on your Desktop. Look for the file called “Install OS X Mountain Lion”, right-click and select Show Package Contents. Once your download is done, go to Finder > Applications. Our goal is here to keep a soft copy of the installer and in the flash drive. Create Bootable OS X Mountain Lionĭo not start the installation process when your download finishes. When you get back, we will look at how you can create a bootable copy of OS X Mountain Lion on your USB drive. Make sure that you won’t need any of the contents of the flash drive, if you do, keep a backup of it somewhere first. While you wait, get a coffee, a break and a USB drive with at least 8 GB capacity. Note that this may take up between 10 and 60 minutes, depending on your Internet connection speeds. If you’ve previously purchased a copy of Mountain Lion, don’t worry, you will not be recharged. Re-enter your App Store credentials if required. Look for OS X Mountain Lion, hold down the Option key and click Download. Launch App Store, and go to the Purchases tab. Here’s how you can download and obtain a soft copy of Mountain Lion. The installer you downloaded fro the App Store automatically deletes itself after you’ve successfully upgraded your Mac. Re-Download Mountain Lionįirst, grab hold of a copy of the Mountain Lion installer file. Recommended Reading: How to Clean Install OS X Mavericks 1. Make a bootable drive of Mac OS X Mountain Lion with a USB drive.

Download a copy of Mac OS X Mountain Lion.

Here is a breakdown of the steps involved: With that cleared up, in this article we will show you how to erase existing data and reinstall a brand new copy of Mountain Lion. A clean install will give you peace of mind.

Two, you are thinking about trading or gifting your machine to someone else, but you are concerned with the remnants of files, profiles and various credentials that if mishandled, may lead to a security leak. To optimize your Mac, it is quite necessary to reinstall and start from a clean slate.

Here are couple of reasons we can think of: One, your existing Mac OS X inherited documents, files and applications that take up a lot of unnecessary storage space. But first, why should you clean install the Mac OS X Mountain Lion at all? Unfortunately in Mac the process can be a little more complicated and less well known. In the Windows’ analogy, this is like reformatting your Macbook or iMac and reinstalling a brand new version of Mac OS X Mountain Lion.

Mac os x mountain lion installer