Want to put the OS X installer onto a bootable flash drive? Apple doesn’t provide an official tool to create bootable copies of their operating system, outside the recovery partition, but a third party tool called DiskMaker makes for a relatively painless process.
Why would you want to do this? Lots of reasons, including if:
- You plan to replace your Mac’s hard drive, so the restore partition isn’t an option.
- You’re building a Hackintosh.
- You need to install/upgrade OS X on a computer without broadband access.
- You want a way to install OS X in case of total hard drive failure.
To get this working you will need: a flash drive with at least 8 GB free, a currently operational Mac, and access to broadband Internet. Let’s get started!
Step 1: Download Your Chosen Version of OS X
The first thing you need to do is download the installer for whatever version of OS X it is you’d like on your flash drive. The only (official) way to do this is using the Mac App Store – I’m personally downloading El Capitan.
You can always find the version of OS X installed on your Mac, and newer versions of OS X, in the App Store by searching. If you’re looking for an older version of OS X, you can find it in the Purchased tab (assuming you’ve downloaded it before).
Once you’ve started the download, you can monitor its progress over on the Purchased tab of the Mac App Store. Versions of OS X are typically sized between 6-7 GB, so the download is going to take a while.
Whatever version of OS X you download, do not follow the installation instructions when the download completes – just close the window and move on to the next step.
Time Machine Users: Potentially Avoid Re-Downloading
Re-downloading OS X might take a long time, especially if the Mac App Store is misbehaving (which, let’s face it, happens a lot). The OS X installer deletes itself after upgrading, which is why you need to re-download the installer to make a thumb drive.
But there’s a potential workaround if you back up your Mac regularly. You hopefully ran a backup before upgrading your OS, and that backup probably includes the downloaded OS X installer.
Check the Purchases tab in the Mac App Store and note the date that you downloaded OS X. Now head to your Time Machine disk in Finder, and browse to the date you just found – then head to the Applications folder within the backup. You should be able to find the installer, as shown above. Just drag that file to your Applications folder, or anywhere you’d like.
Step 2: Install Diskmaker
The next step is simple: head to DiskMakerX.com and grab the latest version of DiskMaker. This free program makes creating a bootable OS X drive simple. Do the usual drag-and-drop-the-icon-dance to install the software.
Step 3: Run Diskmaker
Now the real magic beings: fire up Diskmaker (if it won’t load, check your Gatekeeper settings). You should be prompted with a choice:
Pick which version of OS X you hope to install from your drive. You’ll then be prompted to pick your drive:
It’s really important that you pick the correct drive, because everything on that drive is going to be deleted – pay attention.
Once you’ve gone through all of the steps, DiskMaker will do its thing – eventually it will ask you for your password, so don’t walk away until you’ve done that.
Step 4: Boot From External Drive
When your drive is done, booting from it is simple. Power your Mac down, then hold the Option key as you turn it on. You should see a selection of drives:
Just pick your drive, and eventually the OS X Installer will open.
You can now install OS X, or use any of the utilities that come with the installer.
Alternative: Install OS X to an External Drive.
Maybe you don’t want to install OS X from a USB drive, but actually boot the entire operating system from a USB drive. Good news: that’s possible.
We’ve outlined how to do this in the past for older version of OS X, but these days Apple themselves offer official instructions for the job, and it’s really simple: just connect an external drive, boot your Mac into recovery mode, then pick your external drive as the installation medium.
Boot Windows or Linux From a USB Key
Of course, OS X isn’t the only operating system your Mac can run: you could also get Linux or Windows running on it. We’ve shown you how to boot a Linux live USB key on your Mac, and there are several ways to boot Windows on a Mac. So if you want something besides OS X and your USB key, you’ve got options.
USB Installation is Great
I plan on partitioning an external hard drive, with one partition capable of installing OS X and the other holding various software installers. With that I should be able to recover from a hard drive failure pretty quickly.
I want to know what you’ll be using your bootable OS X key for. Let me know, along with any questions you have about the process, in the comments below.