How to create an OS X flash drive installer

Jason Snell Dan Frakes Chris Breen and Lex Friedman
30 May, 2011
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Faster with flash storage

If you’ve ever had to reinstall OS X, chances are you’ve used the Apple-provided system installer disc that came with the Mac. But what do you do if you misplace the DVD, or it becomes unreadable, or worse—your SuperDrive isn’t working? Having a backup of your system installer disc could save your bacon.

Instead of simply copying the system installer to another disc, you can create a USB flash drive installer similar to the one provided with the latest MacBook Air.  You’ll get an installer that won’t scratch, is easier to transport and considerably faster than an optical disc. We found the install time decreased by 33 percent when using the flash drive method.

The process of creating a flash drive system installer is simple. You’ll need the original installation disc, a working DVD drive and a flash drive with a minimum of 8GB of storage capacity for Snow Leopard (or 9GB if using Leopard, since it calculates file sizes differently). Any data you have on the flash drive will be erased during the process, so back up anything on there that’s important to you.

Step 1: Disk Utility

Plug in the flash drive and once it has mounted, open Disk Utility (/Applications/Utilities). In Disk Utility, highlight the flash drive (not the partition on the flash drive listed beneath it), and select the Partition tab on the right.

Step 2: Partition

Under Volume Scheme, choose 1 Partition as your partition scheme, or if you have a flash drive with enough space, you can create multiple partitions—just be sure that you create one partition that is at least 8GB in size.

Step 3: GUID Partition Table

Once you’ve defined your partitions, highlight the 8GB partition and click on Options underneath it. Select GUID Partition Table and click OK. This lets the computer boot from the drive, so make sure that’s what you pick.

Step 4: Apply settings

Back in the Partition window, under Volume Information, give your flash drive partition a new name. We went with OS X Installer, since that’s basically what it will be and next to Format, pick Mac OS X Extended (Journaled). Click Apply, select Partition from a drop down window and wait for the formatting process to finish.

Step 5: Disk Utility Restore

Pop in your OS X install DVD and wait for it to mount. Once it appears on the left hand side in Disk Utility, click on the Restore tab. Highlight and drag the install DVD into the Source file path on the right.

Now, highlight the flash drive partition, underneath the name of the actual flash drive and drag that to the Destination file path. When you’re ready, click Restore and wait until Disk Utility copies the installation files from the DVD to the flash drive.

Step 6: Boot from the flash drive

When Disk Utility is finished, the flash drive should mount, and you should see the OS X install window appear.

Just to make sure it’s bootable, eject the install disc, but leave the flash drive installer plugged in. Restart your computer while holding down the Option button on your keyboard. You should see two choices to boot from: the hard drive and the Mac OS X Install disc (the icon will be of a USB device). Select the USB drive icon and wait. If you’re greeted by the select a language screen at the beginning of the OS X install process, congrats—you now have a working flash drive installer of OS X.

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