OS X Lion and its downloadable installer create a conundrum for Mac users who would like to have bootable media from which to install Lion.
The reason many people want to have a bootable Lion installer is to create clean installs, that is, install Lion on a freshly formatted hard drive that doesn't contain any previous OS. The other major reason to want a bootable Lion installer is for emergency booting and repair of your Mac's hard drive. It's true that Lion creates a bootable Recovery Partition that you can use for troubleshooting. But the Recovery Partition is only usable if your drive is in basic working order. If your drive has a corrupt partition table, or you've replaced the hard drive, then the Recovery Partition is downright useless.
Since we have valid reasons for wanting a bootable copy of the Lion installer, we're going to show you how to create one using a USB flash drive. If you would rather create a bootable DVD of the Lion installer, we've got you covered there, too. Take a look at:
Create a Bootable DVD Copy of OS X Lion Installer
If you're ready to create a bootable USB flash version of Lion, then let's continue.
What you need:
- OS X Lion installer. This is available from the Mac App Store.
- 8 GB USB flash drive. You can use a larger drive if you wish, but more important than the size of the flash drive is its speed. If you're buying a new flash drive just for Lion, I recommend buying one of the fastest available. While slow (read: inexpensive) flash drives will work fine, you'll find that both the time it takes to create the bootable flash copy of the OS X Lion installer, and the time it takes to install Lion on a target drive, will be somewhat long.
- Some free time. The creation time varies by the speed of the USB flash drive, but plan on 30 minutes to over an hour.
Let's get started.

