Un-check all of the items except “Essential System Software.” You may choose to check “Rosetta” and “QuickTime 7” since they are so small and might come in handy. Click on the Customize button and a new window will appear.Click the Show All Disks button and select your USB flash drive.Enter a name for the volume (I called mine “OS X USB”), select “Mac OS Extended (Journaled)” as the Format, and make sure the size is somewhere around 15-16GB. Go to the Partition tab and select “1 Partition” from the Volume Scheme menu.Open Disk Utility (Applications > Utilities) and click on your flash drive in the list on the left.Make sure there’s no valuable data on there because it will be permanently wiped out in a couple minutes. To start things off, connect the USB flash drive to your Mac.And the third thing you’ll need to get the job done is your OS X installation DVD. While they should be fine, squeeze those versions of Mac OS X on a 16GB drive at your own risk. Keep in mind 10.6 Snow Leopard was used to demonstrate this tutorial, so I’m not sure how much space 10.5, 10.4, and earlier require. Second, at least a 16GB USB flash drive, such as this SanDisk Cruzer Micro for about $30 at Amazon. First you’ll need an Intel-based Mac from the past few years. Now that you’re convinced, let’s figure out how to do this. Your Mac’s hard drive is completely dead and you’d like to use your computer for basic tasks like email and web browsing while you wait for your new drive to arrive.A software problem is plaguing your Mac and you’d like to see if you can replicate it in an isolated environment.The file system on your startup disk has become corrupt and needs to be repaired.Your Mac isn’t starting correctly and you’re not sure if the internal hard drive is failing or if another piece of hardware is to blame.

Not sure when having OS X loaded on a flash drive would come in handy? Here are just a few examples:

It turns out a tiny USB flash drive serves as a great alternative. That means carrying around a bulky external hard drive with cables is not always ideal. And since most Mac owners use a MacBook of some kind nowadays, portability is a valuable thing. A clean installation of the operating system can help pinpoint problems and will come to the rescue in a bind. One of the maintenance tools every Mac user should have available in case of emergency is a bootable copy of Mac OS X on a removable device. All you need to do is carry around a single USB flash drive to be ready for situations the require you to diagnose, repair, or experiment with Mac OS X. Although Macs are reliable machines, they are not exempt from hiccups.

Mac os x bootable usb