When you install or upgrade to Mac OS X Lion, a Recovery HD volume is created on your Mac hard disk as part of the setup. The Recovery HD allows you to reinstall Lion, access Disk Utility, restore from Time Machine backup or browse the web with Safari.
Apple has released Lion Recovery Disk Assistant software, allowing you to create the same Recovery HD volume on an external USB disk or thumb drive. This is useful if your Mac hard disk is not usable or you are replacing the internal hard disk.
Creating the external USB Recovery HD volume is also an alternate way for you to have a clean install of Mac OS X Lion, instead of manually creating the boot disk.
In order to create the external Recovery HD, your Mac’s hard disk must have an existing Recovery HD. The external USB hard disk or thumb drive must have at least 1GB of free space. The Recovery HD volume on your external USB drive is not visible in Finder. To boot from the USB external drive, hold down Option key while Mac is booting, and select the Recovery HD from the boot up screen.
Apple has also created a knowledge base article describing more about Lion Recovery Disk Assistant. The article noted:
- If the computer shipped with Lion, the external recovery drive can only be used with the system that created it.
- If the system was upgraded from Mac OS X v10.6 Snow Leopard to Lion, the external recovery drive can be used with other systems that were upgraded from Snow Leopard to Lion.