You may have noticed that recent Macs don't come with a recovery/install DVD for reinstalling the Operating System in the event of a system crash. In fact, most of them now don't even come with a DVD drive, even if you had a recovery DVD. Instead, they are designed so that the user can reinstall the Operating System via the Internet. That's great, but doesn't always work in every situation. For example, if you're traveling and have a slow connection in your hotel, it could take days for the installation file to download. For this reason, I strongly recommend making your own recovery utility (not that I expect you to use it very often, but when you need it, you will thank me for encouraging you to have one of your own).
There are two steps to making your own bootable OS X Mountain Lion recovery disk:
Step 1) download the Mountain Lion installer file
Step 2) prepare the bootable disk
Before beginning, you will need either a thumb drive or an SD card, at least 8 GB in size. Warning: the below steps will permanently delete anything on your thumb drive or SD card, so make sure you don’t need it. If you don’t have one, you can pick one up for very cheap at your local Best Buy.
Here is a little more detail for you on each of the steps:
Download the Mountain Lion Installer File
To do this, you will first need to go to the Mac App Store and download Mountain Lion (link). AFTER the download has finished but BEFORE you install anything (you actually won’t install what you just downloaded), go to the Applications folder in Finder, right-click on the file called “Install Mac OS X Mountain Lion” and choose “Show Package Contents”. From here, go to the “Contents” folder, then “SharedSupport”. Find the file called “InstallESD.dmg” and place a copy of the file on your Desktop.
Prepare the Bootable Disk
There are a few different ways to do this using tools built-in to OS X Mountain Lion, but I prefer to make things easy on myself. Fortunately, others feel the same way and there is a FREE utility that essentially automates this process for us. You can download Lion DiskMaker here.
When you’re ready, insert your thumb drive (or SD card) and launch Lion DiskMaker. The first thing it will do is ask which recovery disk you want to make (Lion or Mountain Lion). Since we are making a Mountain Lion recovery disk, we will choose “Mountain Lion”.
The next step is to point Lion DiskMaker to the Mountain Lion installer file you just copied to your Desktop. To do that, click “Select an Install file...” and point it to the “InstallESD.dmg” file.
On the next screen, you will choose to “Create a boot disk”. If you are using an 8 GB thumb drive, choose that option. If it’s a thumb drive larger than 8 GB or an SD card of any size, you will want to choose “Another kind of disk”, then choose the name of the thumb drive or SD card.
After that, Lion DiskMaker will begin the process of creating your very own bootable recovery disk (the process takes 3 - 5 minutes to complete).
When you’re done making your recovery disk, label it and store it in a safe place. I have two copies (you can never be too prepared): one on an SD card and one on a thumb drive with my car keys.