Mon 6/6 Installing Lion Clean

lion-install

Now that we know that Mac OS X 10.7 Lion will debut in July exclusively for the Mac App Store a few questions arise.

  • How will customers upgrade Macs running Leopard or Tiger where the Mac App Store is not available?
  • How will customers perform a clean upgrade of Lion?
  • And how will IT departments install Lion across multiple Macs?

The answer to these questions is a Mac First Aid Kit, a specially formatted external hard drive that contains the required operating system and software to install Lion onto any compatible Mac. All it takes is seven easy steps.

(For best results you want to use an external drive formatted with a GUID partition scheme. From Disk Utility select the drive you wish to use in the left hand source pane, and choose the partition tab. The options button allows you to specify the GUID partition scheme. Click Ok, and then Apply to reformat your drive.)

  1. Purchase and download Lion from the Mac App Store on any Lion compatible Mac running Snow Leopard.
  2. Right click on “Mac OS X Lion” installer and choose the option to “Show Package Contents.”
  3. Inside the Contents folder that appears you will find a SharedSupport folder and inside the SharedSupport folder you will find the “InstallESD.dmg.” This is the Lion boot disc image we have all been waiting for.
  4. Launch Disk Utility and go straight to the restore tab. Drag “InstallESD.dmg” the Source field1, and drag your 8GB or larger external hard drive from the left side of the Disk Utility window into the Destination field. Check Erase Destination, and begin your restore. (It goes without saying this process will erase everything on your external hard drive.)
  5. Once Disk Utility’s restoration is complete you will be the proud owner of a Mac First Aid Kit capable of booting and installing Lion clean. Test out your creation by restarting any Lion compatible Mac while holding the option key, and choose Mac OS Install ESD as the startup volume.
  6. Once booted from the Lion enabled partition on your external drive ou will have the opportunity to run Disk Utility and erase your Mac’s primary hard drive. From the Erase tab select your Mac’s primary hard drive and choose “Mac OS Extended (Journaled)” as the format. Before you erase the drive confirm you have a known good backup then click Erase.
  7. With your Mac’s primary hard drive wiped clean it is now time to begin installing Lion. Quit Disk Utility to go back to the Lion installer. Choose your Mac’s primary hard drive as the destination, and continue.

When the installation process is complete your Mac will have a clean copy of Lion installed on its primary hard drive, and you will have an Mac First Aid Kit suitable for installing Lion on other Macs in the future.

It is important that you burn your Lion boot disc or backup the Lion installer prior to installing Lion itself. If left in the Applications folder the installer will be removed after the Lion installation is completed. If you are reading this article after upgrading to Lion all is not lost. A fresh copy of the Lion installer can always be re downloaded from the Mac App Store by clicking on the Purchased tab with the Option key held down.

Shipping software costs money, burns fuel, and requires a trip to the store. By releasing Lion exclusively though the Mac App Store Apple is saving money, reducing its carbon footprint, and giving its customers convenience. Customers who own a MacBook Air or Mac mini server will benefit most from the lack of installation media because Apple saw it fit to ship these computers without a built-in optical drive. Performing a clean install of Lion is not required, but with an external hard drive it is easy to do across multiple Macs.

Want to burn a Lion Boot Disc? It’s easier than you think.


  1. Snow Leopard users will want to mount the “InstallESD.dmg” prior resotring and drag the mounted “Mac OS X Install ESD” into the Source field.