How to Create a Bootable Flash Drive for Installing OS X Lion

Make your own Lion Installer on a USB drive

Mac laptop with an OS X Lion bootable USB stick inserted

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Starting with OS X Lion, Apple did away with DVDs and other media as a method of installing software and switched to a download model instead. Even so, it's still easy to create a USB installation disk for OS X Lion if you want to install Lion on a freshly formatted hard drive, if you're in an emergency booting situation, or if you need to repair your Mac's hard drive.

Here's how to create a bootable flash drive using the OS X Lion installer.

The information in this article pertains only to Mac OS X 10.7 Lion used with at least an 8 GB flash drive that has been formatted for Mac use.

Putting a Bootable Lion Installation on a Flash Drive

This process has a few steps. First, make sure your USB drive is formatted for use with a Mac, then download the OS X Lion installer from the App Store and copy it to your flash drive. Finally, use your bootable flash drive to install Lion on your Mac.

Make Sure Your USB Drive Is Formatted for a Mac

Not all USB drives can be used with a Mac right out of the box. If your USB drive doesn't specifically state that it's Mac-compatible, you'll have to erase and format your drive for use with a Mac. Here's how:

This process will erase any data currently on the USB drive.

  1. Insert the USB flash drive into your Mac's USB port.

  2. From Applications/Utilities, launch Disk Utility.

  3. In the Disk Utility window, select your flash drive in the list of attached devices.

  4. Select the Partition tab.

  5. Use the Volume Scheme drop-down window to select 1 Partition.

  6. Enter a name for the volume you're about to create, for example, Mac OS X Install ESD.

  7. Make sure the Format drop-down menu is set to Mac OS X Extended (Journaled).

  8. Select the Options button, choose GUID as the Partition Table type, and then select OK.

  9. Select Apply.

  10. Disk Utility will ask if you're sure you want to partition your USB flash drive. Select Partition to continue.

  11. Disk Utility will format and partition the USB flash drive. When it's finished, select Quit Disk Utility. Your USB flash drive is prepared for the OS X Lion installer process.

Download OS X Lion and Copy It to Your Flash Drive

Now that your USB flash drive is prepared, move on to downloading OS X Lion and copying the installer to the drive.

  1. On your Mac, go to the App Store and search for Lion.

    Screenshot of Mac App Store downloading OS X Lion installer
  2. Select Mac OS X 10.7 Lion.

    Mac OS X 10.7 Lion costs $19.99 to download.

  3. Select Add to Bag and then complete your purchase.

    Screenshot of purchasing your OS X Lion installer
  4. Apple will email you a redemption code for the Mac App Store. When you receive the email and code, you'll be able to download OS X Lion to your Mac.

  5. Once downloaded, go to the Applications folder and find the copy of Lion.

  6. Right-click on the downloaded file and select Show Package Contents.

  7. Open the Contents folder.

  8. Open the SharedSupport Folder.

  9. Within the SharedSupport Folder is an image file called InstallESD.dmg.

  10. Right-click the InstallESD.dmg file and select Copy from the pop-up menu.

  11. Close the Finder window.

  12. Right-click in a blank area of the desktop, and select Paste Item from the pop-up menu. You've now created a copy of the InstallESD.dmg file on the desktop.

  13. Plug your properly formatted USB drive into your Mac.

  14. Launch Disk Utility.

  15. Select the flash drive device (not the volume name) in the Disk Utility window.

  16. Select the Restore tab.

  17. Drag the InstallESD.dmg file from the device list to the Source field.

  18. Drag the Mac OS X Install ESD volume name from the device list to the Destination field.

  19. Make sure the Erase Destination box is checked.

  20. Select Restore.

  21. Disk Utility will ask if you're sure you wish to perform the restore function. Select Erase to continue.

    You may be asked for your administrator account password; supply the necessary information and select OK.

  22. The clone/restore process can take a bit of time. Once the process is complete, quit Disk Utility.

Using the Bootable Flash Drive

To use the bootable flash drive as an OS X Lion installer:

  1. Insert the USB flash drive into one of your Mac's USB ports.

  2. Restart your Mac.

  3. When your Mac's screen turns off, hold down the Option key while your Mac reboots.

  4. You'll be presented with the OS X Startup Manager, listing all bootable devices attached to your Mac. Use the arrow keys to select the bootable flash drive you created, and then press Return.

  5. Follow the on-screen instructions to install OS X Lion on your Mac.