Apple supplied what it called “Security Test Update Test 1.0.”

Apple supplied what it called “Security Test Update Test 1.0.”

Once you’ve purchased and downloaded the Mountain Lion installer, here are the simple steps involved:

1. Double-click the Install OS X Mountain Lion app; in the window that appears, click Continue, and then click Agree to agree to the software license agreement.
2. On the next screen, you choose where to install the OS. By default, only your internal startup drive is listed; if you have other drives connected and want to install Mountain Lion onto one of them, click the Show All Disks button and then choose the desired drive. Note that the installer will let you choose any drive that has OS X 10.6.8 or later installed or any blank drive—the latter is what you would choose if you wanted to do a "clean" install that contains none of your data, applications, or settings from your current installation of Snow Leopard (OS X 10.6) or Lion. In either case, the destination drive must also be formatted as Mac OS Extended (Journaled) and use a GUID Partition Table; the built-in drive on any Mac eligible to run Mountain Lion should meet these requirements. to help you decide if it's something you want to do.
3. Click Install, and then provide an admin-level username and password when prompted.
4. The installer will spend some time preparing for installation; over many test installations on several different Mac models, this process rarely took more than a few minutes. You'll see a message in the installer window that your computer will restart automatically; you can continue to work in other applications during this time, but once the preparation phase is finished, you’ll get only a 30-second warning, and then your Mac will indeed restart on its own.
5. After your Mac restarts, the actual installation occurs. During my test installs, this process took roughly 15 to 25 minutes, depending on the Mac. (Note that if you’re upgrading from Lion and you have FileVault 2 enabled, when the installer restarts your Mac, you’ll need to provide an authorized username and password to bypass the FileVault lock screen at startup. Once you do, installation will continue normally.)

That’s it—unlike previous OS X installers, Lion's doesn't make you decide what kind of installation you want to do, which language translations or printer drivers to install, or whether or not you’ll ever use X11 or QuickTime 7. The installation procedure is easier and quicker than ever.