Make a Bootable USB Drive of OS X 10.8 Mountain Lion fromthe Recovery Hard Drive

On every OS X 10.8 Mountain Lion there is a hidden partition to enable a method forMountain Lion OS to be reinstalled on the machine, it is known as the Recovery Par-tition or drive and is 650mb in size.

If you bought a new machine from Apple you have OS X 10.8 already installed – butno back up disk! and since you haven’t bought the OSX Lion 10.8 App from the Appstore you can’t re-download it – so thats why you have the recovery drive as a parti-tion in your main hard drive, to boot from it you need to restart the machine andwhen it starts to boot hold down “command” + “r” keys.

From the Recovery Partition Hard Drivr you can run Disk Utility, access the com-mand line, get online help and do a restore from a Time Machine backup and re-in-stall Mountain Lion leaving all your other files intact – it just replaces the core oper-ating system.

You can make a bootable USB drive or disk from the Recovery Partition 2 ways – theeasy way and on the Terminal

The Easy Way

1) Download OSX Recovery Disk Assistant and uncompress and launch it

2) Attach the USB drive that you want to copy the Recovery Partition to.

3) Select the drive and continue (All contents on it will be erased)

That’s it one external bootable Recovery Drive – this works on both OSX 10.7 and 10.8

The Terminal Way

1) Launch Terminal from /Applications/Utilities and run:

diskutil list

The main drive in this list is No.2 with the “Identifier” of disk0s2, the boot RecoveryHD drive is disk0s3

disk-util-list-drives

We can also identify the Recovery drive by the name and the size – set at 650mb

2) Mount the drive by its Identifier:

diskutil mount /dev/disk0s3

Output should be:

Volume Recovery HD on /dev/disk0s3 mounted

Now the Recovery HD is mounted in the Finder and you can see it in the sidebar un-der DevicesNavigate to it from the sidebar – Recovery HD/com.apple.recovery.boot/BaseSys-tem.dmg

recovery-finder-osx-lion

3) Doubleclick BaseSystem.dmg to mount it also in the sidebar. This will mount thevolume ” Mac OSX Base System”

basesystem-recovery-drive

macosx-basesystem

4) Open Disk Utility in /Applications/Utilities

5) Put in a 2GB+ USB drive, let Disk Utility load it. The USB drive needs to be format-ted as Mac OS Extended Journaled, if its not, its time to format it in Disk Utility…

usb-format-osx-extended-lion

6) Finally in still in Disk Utility, select the “Restore” tab - drag the mounted volume“Mac OSX Base System” into the Source field and drag the USB drive “Volume”(mine is called SuperBootUSBDrive) to the Destination.

restore-volume-osx-usb

7) Click Restore – 10 minutes later – One bootable USB drive

Your bootable USB drive will be called “Mac OS X Base System” after the restore iscomplete. Now to boot from it just select it as the Start Up disk in System Preferencesor hold down option key on boot and select it from the choice of bootable devices.

start-up-system-preference

If you have downloaded the OSX 10.8 Mountain Lion App from the App Store thenyou can also make a full bootable image of OSX 10.8 to a disk/drive, you need tomake the boot drive/disk before you install the Mountain Lion App, as the installer isdeleted after running it. That’s why the guide here can get you out of trouble.

Update For Newer Models – hidden BaseSystem.dmg - BaseSystem.chun-klist

If you have the latest models from Apple that came already shipped with OSX 10.7,then you may not have the “BaseSystem.dmg” but instead see a “BaseSystem.chun-klist” , the “BaseSystem.dmg” is there it’s just hidden.

To show it so you can see it in the finder – go to Terminal – and after you havemounted the Recovery Drive:

cd /Volumes/Recovery HD/com.apple.recovery.boot

sudo chflags nohidden BaseSystem.dmg

Now it will be visible in the Finder.

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