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Quick Tip: How and Why to Change Your Mac's Startup Disk


Your Mac has the ability to boot into any form of storage connected to it, which is a huge benefit in some situations. Whether you've got a Mac hooked up over Thunderbolt and want to boot into it or have re-install/recovery media, OS X's built in tools to change your startup disk are pretty handy and straightforward. Let's take a look!

Why Would I Want To Do That?

There's a number of circumstances when you might want to boot into a different storage volume. The ones I find most common in my use include:-

  • Recovery and Reinstallation - If you're looking to recover or reinstall OS X, you can use these tools to boot into your Lion/Mountain Lion startup volume or any physical recovery media you have connected to your computer (such as an included DVD or USB drive).
  • Booting with Target Disk Mode - If you've got a Thunderbolt cable and plan to use Target Disk Mode, you will need these tools if you want to boot into another Mac's hard drive. This way, you can run Mac A's version of the operating system and access Mac A's files on Mac B's hardware, something I like to do when I'm at my desk with both my Mac Mini and MacBook Air.
  • Boot Camp - You'll need to use these tools to choose whether to boot into OS X or Windows, as needed or by default.
  • Multiple Versions of OS X - It's not out of the question that you might want to have two copies of OS X for compatibility reasons, so these tools can be used to choose which version to boot into.

One Time Only and On Demand

If you just happen to want to switch your startup disk once or otherwise don't want to change the default, there's a pretty simple way. Simply restart your Mac and hold the Option key until a selection screen appears.

Simply restart your Mac and hold the Option key until a selection screen appears.

Here, you can select any of the bootable storage and media volumes connected to your Mac, including your OS X recovery partition. Simply using the arrow keys you can select a partition by name or type. Rinse and repeat whenever you want to switch.

This process doesn't change your default startup disk, however. So, if, for example, you boot into a Windows partition while your default startup disk is still running OS X, a restart without holding down the Option key will still result in you booting OS X.

Bonus: BootChamp

If you've got a Boot Camp partition, there's a particularly useful app for OS X to help simplify the process of booting into a Windows partition.

BootChamp is a very simple utility suggested by a reader that sits in your menu bar and gives a two-click process of restarting your Mac and automatically booting into your Windows partition. It's free too!

Changing The Default

If you would prefer to not boot into the Startup Manager (the process laid out in the previous section) every time and would find it more convenient to simply change the default, it's a painless process.

Simply head to System Preferences and select "Startup Disk." Then it's just a matter of selecting the storage volume you want to boot into by default, identifiable by icon, name and/or operating system listed. You can leave that for the next time you reboot or just hit the "Restart..." button to boot into your new default immediately.

The same can be done in Windows through the Boot Camp Preferences app, and requires the same process.


It's that simple. Using multiple startup volumes can have numerous benefits and uses, whether it be keeping a copy of Lion on an external drive in case you want to go back in time or simply want to use Bootcamp.

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