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:
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.
Using the Bootable Flash Drive
To use the bootable flash drive as an OS X Lion installer: