How to Install Mac OS X From a External Hard Drive

By Art Corvelay

There may be several reasons that you want to install Mac OSX from an external hard drive. You may want to restore your operating system back to its original settings. Regardless of the reason, this article will walk you through some basic steps for installing the Mac OSX from an external hard drive.

Things You'll Need

  • External HD with OSX disk image

Step 1

Plug in your external hard drive and open up "Disk Utility." It will most likely be located in your "Applications>Utilities" folder.

Step 2

Click on your external hard drive. If your computer recognizes your external hard drive, it should appear on the left hand menu of the disk utility application.

Step 3

Click the "Restore" tab. There will four tabs running across the top of "Disk Utility." "Restore" is the tab on right-hand side.

Step 4

Click the image tab located directly to the right of the source field. You will choose the disk image, for example "tiger.dmg," that you would like to install.

Step 5

Drag your external HD into the "Destination" field. Your external HD should be located in the left-hand pane. Simply click and drag your external HD into the destination field and click "Restore." The restore process should begin and may take up to a few hours, depending on your system hardware.

Step 6

Open "System preferences" once the restore has successfully completed. To do this, click the apple icon in the upper right-hand corner of your screen and choose "System preferences."

Step 7

Click on "Startup disk." It will be an icon located under the "System preferences" menu.

Step 8

Select the external hard drive. This will be the drive in which you recently installed the OS disk image.

Step 9

Click "Restart" and the Mac OSX will begin installing from the external hard drive.