If you’re thinking about the other disk drives pictured, it’s because I’m booting up a double Lion and a snow leopard, and “Recovery HD” is a small recovery partition that Lion installs alone. Here you can format, restore from backups, or reinstall Lion. Here’s what you see on startup when the drive is connected: When this is done, the bootable Mac OS X Lion installer is ready! You can now boot from any USB drive on your Lion-compatible Mac, just plug in the USB key, hold down the Option key during startup, and select the drive. Now you wait for the Lion DMG to be restored to the USB drive, this may take a while and you will see a screen like this: Make sure you have the right things in the right places, you don’t want to format the wrong drive – then click Restore.Drag a formatted USB key to Destination and check “Delete Destination”.That’s why we installed the InstallESD.dmg file before, because we can only drag and drop the “Source” image of the “Mac OS X Install ESD” image – if you didn’t install the image, you can find and select the image file by clicking “Image” Now you need to specify the recovery source.In the Disk Utility, right-click the USB drive, and then click Restore.Now that the USB flash drive has been formatted to the appropriate file system, we are going to restore the previously installed InstallESD.dmg file to an empty USB drive. Select “Mac OS Extended (Journaled)” as the format, and name the USB key with the name you want.

Select the USB drive on the left side of Disk Utility, and then click the Delete tab.Next we format the USB memory stick, this will launch the Lion installer: Double-click “InstallESD.dmg” to install the Lion disk image on your Mac desktop, it will look like the image below.

Mac os x mountain lion iso usb bootable