How to restore a missing Recovery HD partition in Lion

When you install OS X Lion, the system will create a hidden partition called "Recovery HD." In addition to providing recovery and diagnostics tools similar to those on the older OS X installation DVDs, it is also used for enabling enhanced features in Lion such as Apple's FileVault 2 disk encryption and the "Find My Mac" location service as part of iCloud.

While this partition should be present on most systems running Lion, in some situations it may be missing. If you've installed Lion on a drive with too many partitions or an unsupported RAID array, then while the Lion installer will allow you to continue the OS installation, it will just omit setting up the Recovery HD partition.

In addition to unsupported drive configurations, you can inadvertently remove the Recovery HD partition if you format your drive and restore from a cloned backup. While block-level cloning of a drive will preserve its partitions and the data on multiple volumes, this cannot be done on the boot drive so an alternative that is more commonly used is file-level cloning that copies all the files from one volume to another. Unfortunately doing this will only copy the files from your OS X installation and not from other partitions like Recovery HD, so if you have cloned your system to an external drive followed by repartitioning and formatting your internal drive and restoring, then you likely will have removed the recovery HD partition.

To see if your system contains a Recovery HD partition, you can restart with the Command-R keys held down. If your system boots to the recovery tools, then the partition is present. Optionally you can enable the debug menu in Disk Utility, followed by selecting "Show every partition" in this menu to see if the Recovery HD partition gets listed in the tool (it should be grayed out).

If your recovery partition is missing, then there are several options you can take to use either it or its functions, but these options will depend on why your partition is missing in the first place:

• Unsupported drive setups
  If Lion was initially not able to create a Recovery HD partition because your drive setup is unsupported, then you will not be able to create the partition on your boot volume. As a result you will not be able to use advanced drive encryption options and iCloud's "Find my Mac" feature; however, you can still create a Recovery HD partition on another drive to use its tools. To do this, you will first need to redownload the Lion installer from the Mac App Store (you can do this by holding the Option key and clicking the Purchases tag, which will give you an option to redownload the installer).
  
  With the installer available, you now have two options. The first is to create an external boot drive from the installation disk image that is contained within the installer, and the second is to simply run the installer and install Lion to a secondary hard drive. When the installation is complete, you can then boot to the new drive and run Apple's Lion Recovery Disk Assistant tool to create a separate recovery thumb drive. Alternatively you can reboot to your main OS installation, run Disk Utility, and then format the new "Macintosh HD" volume on your secondary hard drive, which will leave the Recovery HD partition there for you to use if needed, while freeing up the rest of the drive for other uses.
  
  With these methods, do keep in mind that you may have to restart with the Option key held down to select and boot from the Recovery HD partition on the attached drive.


• Supported drive setups
  If your system initially had a recovery partition but after cloning and formatting it is no longer available, then one method of getting it back is to simply download and reinstall Lion from the Mac App Store. Doing this should keep your data and installed applications intact, but result in a fresh local Recovery HD partition installed along side your OS installation.


• 2010 Macs or later
  If you have a newer Mac system, then as long as you have the latest firmware updates installed you should be able to use Apple's Internet Recovery feature and can bypass the need for a local Recovery HD partition. Apple recently released new EFI firmware updates for mid-2010 MacBook and Mac Mini systems that enable Internet Recovery, but there are also updates available for newer 2011 Mac models that do the same thing. With the Internet Recovery enabled in the Mac's firmware, to use it you just need to restart with the Command-R keys held down. If there is no local Recovery HD partition available, then the system will ask you to join a network. You will need a Wi-Fi connection available that is secured with a WPA or WPA2 password (other forms of connection such as WEP and certificate-based authentication will not work), and then the system will download and boot from a recovery image file obtained from Apple's servers.

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