Pin Me

How to Clean Install Mac OS X 10.7 Lion

written by: Nicholas•edited by: Michael Dougherty•updated: 7/31/2011

Although Mac OS X Lion is intended to be installed from Snow Leopard, it can be clean installed as well. For many Mac users, this may be the best option, particularly if there are a bunch of junk files that Snow Leopard has collected.

  • slide 1 of 6

    Getting Started...

    Whenever a new operating system is released, many users prefer to start fresh, rather than upgrading an old operating system. These types of install gives you the advantage of having a pristine operating system to work with, without any incompatible files from a previous OS. It may also give you a very slight increase in speed, because the operating system will be fresh. For example, several upgrade installs stacked together may eventually begin to slow your system. As a further example, if you started with Mac OS X Leopard, than upgraded to Snow Leopard, than upgraded to Lion, you may have noticed that Mac OS X doesn't run nearly as quick as it use to. This is because upgrade installs tend to leave files from previous operating systems around, although they are not really needed. With a new Mac OS X Lion install, you will get the files you need, and only the files you need.

    This type of install can also save you time. If you were to purchase a new hard drive, you would not want to have to install Leopard, then Snow Leopard, then Lion, simply because Snow Leopard and Lion were intended to be "upgrade only."

    Previously, I wrote a post on how to clean install Mac OS X Snow Leopard, which I believe worked out well for many people who attempted it. Although the install process is similar, Lion's new UI requires a couple of modified steps, in order to complete correctly. The following paragraphs detail these steps...

  • slide 2 of 6

    Before The Install

    Hard copies of Mac OS X Lion are not going to be distributed by Apple, meaning no install DVDs with new Macs and no retail DVD distributions. However, Apple has stated that they are going to release USB flash drives for $69.00 in August. The problem with that? You probably want to purchase Lion now, and Lion in the App Store is only $29.99. Once you have purchased and downloaded Lion from the App Store, you will need to create a backup DVD or USB flash drive in order to perform a clean install. Our guide to creating backup media for Lion will help get you started.

  • slide 3 of 6

    The Clean Install

    Clean Install Mac OS X Lion

    • Insert Mac OS X Lion install DVD or USB flash drive into computer's SuperDrive or available USB port.
    • Wait for the install DVD or USB drive to appear on desktop or within Finder, assuring a proper connection.
    • Restart the computer.
    • Immediately upon reboot, as soon as you hear the start up chime noise, hold down the option(alt) button on the keyboard. Continue to hold the button until the boot screen appears. This screen will list your internal Mac hard drive (usually Macintosh HD), as well as any other bootable drives or partitions that are connected. More importantly, this screen should give you the option to boot from your Mac OS X install DVD or USB drive.
    • Arrow over to the Lion install DVD or USB drive and hit the enter key on the keyboard.
    • Upon booting from DVD or USB, the Apple logo should appear, and you will have to wait for the media to load up.

    *If you are unable to boot from DVD using the option key, try holding down the "c" key at bootup instead.

    • Once the welcome screen appears, click Continue to confirm that you want to proceed to Mac OS X Lion setup.
    • At the next screen, you will be presented with a couple of different options. Select the Disk Utility option.
    • Once Disk Utility launches, select your hard drive from the left hand side drives list pane.
    • Click the erase tab.
    • You can choose to erase your hard drive using a quick format or a more secure erase. To use the secure erase option, which erases your data and writes over it, click security options and select Zero out disks. If you simply want to reformat your hard drive and clear data, use the erase option. The "Erase" method is much faster, and because you are not selling the hard drive or your computer, there is not as much of a need to zero out the data.
    • Before erasing, assure that the drive format is set to "OS X Extended Journaled." You should also enter a name for the drive, which will be used to identify the hard drive. By factory default, the name should be "Macintosh Hard Drive." Click erase to format the hard drive and delete any old files. Once the erase completes, all of your previous data will be gone.
    • Select the disk utility option located on the top navigation bar. Select "Quit Disk Utility" from the drop down menu. OS X will return to the main installation screen. Select the Reinstall option to clean install Mac OS X Lion.

    The on-screen prompts will guide you from here, and it is basically a wait now, for Lion to finish installing.

  • slide 4 of 6

    Recovering iLife Software

    Once Lion finishes installing, you may notice that your iLife software (iPhoto, iMovie, iDVD, etc...) did not install. That is okay, because it is not included with Lion. iLife can be restored using the discs that came with your computer. In most cases, depending on which Mac you have, you will need to use disc 2, or the applications disc. This disc should give you the option to install bundled applications.

  • slide 5 of 6

    Lion Recovery Options

    Once Lion is installed onto your computer, you can use the new recovery feature, to repair or reinstall Lion at any time. Simply restart your computer. When the computer starts booting back up, hold down the Command-R buttons to boot into recovery.

  • slide 6 of 6


    1. Author's experience with installing Mac OS X 10.7 Lion.