If you have multiple bootable partitions on your Mac, such as the case when you create a separate partition for testing a new OS, you’ll need to know how to manage your Mac’s startup disk.
The startup disk is the disk that the Mac boots from when restarting your computer. You can change this disk permanently, or change it on a temporary case-by-case basis.
In this tutorial, I’ll show you how to establish a set startup disk, and how to change the startup disk on the fly as you reboot your Mac.
How to permanently set your Mac’s startup disk
Step 1: Open System Preferences.
Step 2: Click Startup Disk.
Step 3: Click the disk that you wish to use as your Mac’s permanent startup disk.
Whenever you reboot your computer, your Mac will always boot to the selected disk. You can change this setting at your leisure.
How to change your Mac’s startup disk on the fly
Step 1: Reboot your Mac while holding the Option (⌥) key on your keyboard to load the Startup Manager.
Step 2: From Startup Manager, click on the disk that you wish to boot from.
That’s all there is to it. I recommend using the Startup Disk option in system preferences if you plan on using a particular disk for an extended period of time, otherwise, it may be best just to temporarily switch disks using the Startup Manager on reboot.
Which option do you use when managing your startup disks?