While there are numerous sites that describe how to create a bootable disc that will allow users to install a fresh copy of OS X 10.8, I found that it takes a little ingenuity to clone an existing 10.8 installation so that it will boot off of an external drive.
Two programs that I’ve used for years for cloning Mac OS X are Carbon Copy Cloner and SuperDuper. On occasion, I’ve also used Apple’s Disk Utility. With the release of Mountain Lion, the developer of Carbon Copy Cloner decided that if users wanted to continue using the latest version of his software program that they would have to pay a license fee (approx. $40). This commercial release (3.5.1) of Carbon Copy Cloner is compatible with OS X 10.8, particularly its ability to clone Mountain Lion’s Recovery HD Partition, while the older donation-ware versions are not. On the other hand, while SuperDuper 2.7.1 claims that it is compatible with Mountain Lion, this tool lacks the means to deal with recovery partitions.
Since I already owned a SuperDuper license, I downloaded and installed the 10.8 compatible version (2.7.1) on my Mac. I then used SuperDuper 2.7.1 to clone my Mountain Lion installation onto an external hard drive enclosure. While SuperDuper claimed that the cloning process completed successfully and I could select this 10.8 system from Startup Disk preferences, my Mac refused to boot off of the external drive.
Undaunted, I then purchased a Carbon Copy Cloner 3.5.1 license and attempted the same cloning procedure. When I opened CCC 3.5.1 to define my backup parameters, the software tool instantly recognized the existence of a Recovery Partition and prompted me to first clone the partition onto my designated backup volume. After I allowed CCC 3.5.1 to clone the recovery partition, I then cloned the 10.8 installation. However, the external drive wouldn’t boot, either, just like what I experienced with SuperDuper.
My third attempt proved to be the charm. I erased the CCC 3.5.1 clone from the external drive and used Disk Utility to restore 10.8. Doing so allowed me to boot 10.8 off the external drive.
If you elect to perform a system clone of this nature, you may also wish to take a few minutes to follow the instructions on an Apple Discussion Board thread which will enable you to view the hidden Recovery HD partition in Disk Utility.
Enable the Debug Menu in Disk Utility
1. Quit Disk Utility if it is open.
2. Launch Terminal, located at /Applications/Utilities.
3. Enter the following command at the Terminal prompt:
defaults write com.apple.DiskUtility DUDebugMenuEnabled 1
4. Press Enter or Return.
5. Close Terminal.
6. Open Disk Utility. From the Debug menu, scroll down and place a check mark next to Show every partition
If you find this tip useful, please let me know!