How to Make a Bootable Mac External Hard Drive

A bootable external hard drive is an exceptionally handy tool for running disk utility software, troubleshooting a misbehaving Mac and for booting off of a USB flash drive. Cloning your internal hard drive is the easiest and most common way to create a bootable Mac external hard drive

Difficulty: Moderately Easy

Instructions

1. 
   Install SuperDuper.

   Download the free SuperDuper application and double-click the application .dmg disk image icon to mount the image file. Once mounted, click and drag the SuperDuper application to your "Applications" folder to copy the application to your Mac hard drive. Close the Super Duper disk image and un-mount the image file from your desktop by dragging the mounted disk image file to the trash.

2. 
   Select the Source and Destination Volumes.

   Double-click the SuperDuper application to launch it. Select your Mac's internal, or source, volume/hard drive in the left-hand pop-up window. Select the external, or destination, volume in the right-hand pop-up menu. There is no need to select any other options, as SuperDuper will automatically format and copy the files on your source drive and make your copied system folder bootable. When you've completed your options, click the "Copy Now" button on the bottom right of the SuperDuper window. This will erase all data on your destination or external drive.

3. 
   SuperDuper Progress Menu

   The SuperDuper progress window will show the completion of the copied bootable Mac drive. Depending on the size of the drive being copied, this can take from a few minutes to a hour to complete. When SuperDuper is finished copying the bootable drive or volume, the new bootable drive will automatically mount on your desktop. To use the new bootable Mac volume, restart your Mac and hold down the "Option" key. You will be presented with the available bootable volumes. Double-click the external drive or volume to boot from that drive.