OS X Mountain Lion Installation Guides

Clean Install, Upgrade Install, and Creating Bootable Copies of Mountain Lion

OS X Mountain Lion supports several different installation options. It may not be evident when you start the Mountain Lion installer, but you can perform a clean install or an upgrade install of the OS.

You can also install Mountain Lion on a wide range of devices, including your startup drive, an internal partition or volume, or just about any external drive you may have.

Another option is to create bootable copies of the installer that can run on a DVD, USB flash drive, or another storage device. This choice lets you keep a version handy in case you need to reinstall your operating system.

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Minimum Requirements for OS X Mountain Lion

OS X Mountain Lion has a few special needs that unfortunately will prevent it from running on some older Intel Macs. Even some Macs that can run OS X Lion may not meet the minimum requirement for Mountain Lion.

Here are the devices that can upgrade to Mountain Lion:

  • iMac: Mid-2007 or newer
  • MacBook: Late 2008 Aluminum; Early 2009 or newer
  • MacBook Pro: Mid-2007 or newer
  • MacBook Air: Late 2008 or newer
  • Mac mini: Early 2009 or newer
  • Mac Pro: Early 2008 or newer
  • Xserve: Early 2009

Having the right device isn't enough, however. Your machine also has some minimum requirements it has to meet:

  • A Mac running OS X 10.6.8 (Snow Leopard) or OS X 10.7 (Lion)
  • At least 2 GB of RAM
  • 8 GB of available space

Getting Ready for OS X Mountain Lion - Check Your Drive for Errors

No matter what method of installation you plan to use with OS X Mountain Lion, one of the first orders of business is to make sure that the target drive is sound, free of errors, and unlikely to fail anytime soon.

Here's how to do a quick check on your startup drive:

  1. Open Disk Utility from the Utilities folder in Applications.

    Disk Utility on a Mac
  2. Click your drive in the left pane.

    A drive in Disk Utility
  3. Click First Aid.

    Selecting First Aid.
  4. Select Run in the window that appears.

    Selecting Run.
  5. A message may appear telling you that your drive will lock while Disk Utility checks it. Read the warning and click Continue.

    Selecting Continue.
  6. First Aid will run and report any issues it finds.

Back Up Your Mac Before You Upgrade to Mountain Lion

In the hurry to update to a new OS, this is another crucial step that individuals often forget. Before you begin the OS X Mountain Lion installation, back up your data and apps. It doesn't matter what backup method you choose. Some popular options are Time Machine, your favorite third-party backup application, or a clone of your startup drive and all of its data.

The important thing is to have a current backup in case anything goes wrong during or right after the installation. Delaying the installation for a few minutes to perform a backup is better than frantically trying to re-create your data because the power went out during the installation process.

How to Perform a Clean Install of OS X Mountain Lion on a Startup Drive

A clean install of OS X Mountain Lion will get you a clean Mac with no old user data or apps; just a fresh start to work from.

You can also install your OS on a non-startup drive. Unlike this process, which requires you to create bootable media first, there are no special techniques required for a clean install on a non-startup drive.

Because the target is the startup drive, you'll have to first erase the drive, which will also erase the OS X Mountain Lion installer. To avoid this catch-22, you should first create a bootable copy of the installer and then use it to install the OS on the blank drive.

Optional: Create Bootable Copies of the OS X Mountain Lion Installer

This optional step creates a bootable copy of the Mountain Lion installer, which is handy to have around. With it, you can perform a clean install of Mountain Lion on your Mac's startup drive, as well as boot from and run Disk Utility and other emergency tools.

You can create a bootable copy of Mountain Lion on any bootable media, including DVDs, USB flash drives, and external volumes.

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