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In the Windows' analogy, this is similar reformatting your Macbook or iMac and reinstalling a brand new version of Mac OS X Mount Lion. Unfortunately in Mac the procedure can exist a little more than complicated and less well known. Merely first, why should you clean install the Mac Bone X Mountain Lion at all?

Here are couple of reasons we tin can think of: One, your existing Mac OS X inherited documents, files and applications thattake upward a lot of unnecessary storage space. To optimize your Mac, it is quite necessary to reinstall and first from a clean slate.

Two, you are thinking almost trading or gifting your car to someone else, but you are concerned with the remnants of files, profiles and diverse credentials thatif mishandled, may lead to a security leak. A clean install volition requite you peace of mind.

With that cleared up, in this article we will show yous how to erase existing data and reinstall a make new copy of Mountain Lion. Here is a breakdown of the steps involved:

  1. Download a re-create of Mac OS Ten Mountain Lion
  2. Make a bootable drive of Mac Os X Mount Lion with a USB bulldoze
  3. Reboot, Clean up and Reinstall

You ready? Let's do it.

Recommended Reading: How to Clean Install OS X Mavericks

one. Re-Download Mount King of beasts

Get-go, take hold of concur of a copy of the Mountain King of beasts installer file. The installer y'all downloaded fro the App Store automatically deletes itself after you've successfully upgraded your Mac.

Hither'south how you can download and obtain a soft copy of Mountain Lion.

LaunchApp Shop, and go to thePurchases tab.

purchase tab

Look forOS X Mount Panthera leo, hold downward the Pick key and clickDownload.

Re-enter your App Store credentials if required. If you've previously purchased a copy of Mountain King of beasts, don't worry, yous will not be recharged. Note that this may take up between ten and sixty minutes, depending on your Cyberspace connexion speeds.

download mountain iion

While you expect, go a coffee, a break and a USB drive with at least 8 GB capacity. Make sure that you won't need any of the contents of the flash bulldoze, if you practice, continue a backup of information technology somewhere first.

When you get back, we will look at how you tin can create a bootable copy of Bone Ten Mount Lion on your USB bulldoze.

2. Create Bootable OS 10 Mountain Lion

Practice not start the installation procedure when your download finishes. Our goal is here to keep a soft copy of the installer and in the wink bulldoze.

Once your download is done, go toFinder >Applications. Expect for the file called "Install Bone X Mountain Lion", right-click and selectProve Parcel Contents.

show package content

Navigate toContents > SharedSupport, then await for the filename "InstallESD.dmg"

mountain lion installer file

Double-click InstallESD.dmg to open/mount information technology on your Desktop. This may take a minute or two.

mount installer

Plug in the wink bulldoze into your Mac and launch theDisk Utility application. Y'all can do information technology quickly by searching via Spotlight.

disk utility via spotlight

In Deejay Utility, practice the following four steps carefully:

  1. Select the USB drive on the left bill of fare,
  2. Select theErase tab,
  3. SelectMac Bone Extended (Journaled) for the format.
  4. Click theErase button.

Note: This volition remove everything in the flash drive. Keep a backup of the files within if you lot however need them, then come dorsum to this section.

format usb as mac extended

In one case the wink drive is formatted, re-select the formatted USB drive from the left menu, and click theRestore tab.

select restore tab

Next, we are going to create a bootable OS X Mount Panthera leo in the wink drive. Do the post-obit steps carefully:

  1. Drag the formatted drive from the left menu to theDestination field.
  2. Drag"Mac OS X Install ESD" on the left menu toSource.
  3. Click theRestore push. Installation may accept about 10 – 20 minutes.

restore source destination

Once it's done you'll have yourself a flash bulldoze with a bootable Mountain King of beasts.

3. Reboot, Clean Upwards And Reinstall

So we've downloaded a new copy of Mountain Lion and made it bootable in a flash drive. Next up, we'll attempt to remove everything from the current OS and reinstall a new copy of Mount Lion.

First, a reboot! Hold downwards the Option key as you restart and you lot'll end up at the screen below. And so, select theMac OS X on the right.

restore source destination

You lot'll exist taken to the Os Ten Utilities dialogue. SelectDisk Utility.

restore source destination

At the Disk Utility screen, make certain you have these selected:

  • You are selecting yourMac'due south hd (and non your flash drive's) on the left menu.
  • You are on theErase tab.
  • You lot have selected the "Mac OS Extended (Journaled)" format.

restore source destination

Click theErase button button and everything (including files, applications, settings, etc) in your Mac will be completely deleted.

Annotation:Practise this with caution every bit there will be no way for recovery from this signal onwards.

(iii.4) When y'all are done, you'll be directed back to theOS X Utilities dialogue. This fourth dimension, selectReinstall OS X, the 2d option from the list.

restore source destination

That'due south Information technology!

Your Mac volition now reinstall from the flash drive and you lot'll end up with a clean slice of Mac OS X Mount Lion OS, as if your MacBook or iMac was make new.