The included Recovery partition in OS X Lion and Mountain Lion provides tools for repairing a damaged hard drive, restoring from backup, and reinstalling OS X if needed, among other options. If your system needs any of these tasks performed, then you can usually load the Recovery partition by holding Command-R at startup. However, there may be times when this will not work, and instead of loading the recovery tools the system boots to the standard OS X installation.
If you find you cannot load the OS X Recovery partition, then there are several things you can look into as possible causes:
- Reset the PRAM
The parameter RAM in the Mac has an option to store boot options, and if this feature is not working properly then it may prevent the system from properly managing such arguments. Therefore, first try resetting the system's PRAM by rebooting with the Option-Command-P-R keys held, and then release them after the system resets and sounds the boot chimes again.
- Using a wireless keyboard?
Often instructions for loading the recovery partition are to simply hold the Command-R keys at startup, which works for laptops and USB keyboards, but requires some additional attention for wireless keyboards. Apple's computers initialize onboard bluetooth controllers at the boot chimes, so if you hold keys down before this then they will not register. Therefore, wait for the boot chimes to sound and then press and hold the Command-R keys (this is true for other startup hotkeys as well).
- Firmware password
Apple's computers come with an option for a firmware password, which adds security by locking out the ability to use alternate boot modes, which include Safe Mode, Single User mode, and the OS X Recovery partition. If you have a firmware password enabled, then when you try to load a secondary boot volume the system will ask you to enter the password. This in itself will be indicative enough that a firmware password has been set, so after supplying it you should be able to boot to the recovery drive.
- Is the partition present?
In some rare cases, the OS X recovery partition may be missing. This may happen if the boot drive is a non-standard setup, such as a software RAID array, or if the recovery partition was manually deleted (ie, through modification of the partition tables with a drive management program).
You can check if the partition is present, by opening the Terminal utility and running the following command:
In the output of this command, you will see the available hard drive volumes listed on a per-device basis. While the output may seem a bit cryptic, you should be able to see the corresponding volume names listed in the middle, and if you cannot find one called "Recovery HD" that is 650MB in size, then the partition is missing.
If you are an iCloud user, then you can also see if the Recovery partition is present by attempting to enable iCloud's "Find My Mac" feature. This requires the recovery partition, and if it is missing then "Find My Mac" will be grayed out in the iCloud system preferences, with a small note that a recovery partition is required.
If the partition is missing, then the only way to fix it -- provided -- is to reinstall OS X. A standard reinstall will not affect your personal data, accounts, installed applications, and other settings, it will only replace your operating system software (though be sure to back up beforehand, just in case). To do this, you will need to use an alternative to the recovery partition in order to run the OS X installer.
The first option is to go to the Mac App Store and download OS X again. This should provide you with an installer which when run should set up the recovery volume again. The second option is to to reinstall, which if you created when initially installing OS X will avoid the need for you to re-download the OS X installation files from Apple. Lastly, if your Mac supports Internet Recovery, then you can use this by holding Option-Command-R at startup instead of just Command-R. This will load the same recovery tools from Apple's servers that are present on the local recovery volume and should allow you to similarly reinstall OS X.