Aside from the default boot drive, your Mac computer can be configured to start up from a bootable CD or DVD, a USB thumb drive, an external drive, a network volume or a different disk.
The process for changing the startup disk differs from Intel-based Macs to Apple silicon ones. In this tutorial, we’ll show you how to change your Mac startup disk for the next boot session only or for all sessions going forward, on both Intel-based and Apple silicon computers.
How to change your Mac’s startup disk
Selecting a startup disk other than your Mac’s default startup drive can be done in two ways:
Changing the startup disk once is only valid for the next boot session. Conversely, changing the startup disk for every startup remembers it across future sessions until you change it again.
Change your startup disk once
You can change your startup disk once by pressing a special keyboard combination at boot time to bring up the startup volume sector, which lets you change your boot volume:
Apple silicon Macs
To change the startup disk on your Apple silicon Mac for the next session only, you must use a special key combination to access your startup disk options.
- With the machine turned off, press and hold the power button until you see “Loading startup options” (on an Apple silicon Mac mini, wait for the system indicator light to turn amber).
- Your Mac will scan all the disks attached to it. With the available startup disks displayed, select one and click the “Continue” button.
The computer will restart using the newly selected startup disk.
As mentioned, this is a one-time change: The next time your computer restarts, it will switch back to using the disk that’s currently selected as your startup disk in System Preferences.
On an Intel-based Mac, you must use access the built-in startup volume manager during boot time to select. different startup disk but only for the next session:
- With your Intel-based Mac turned off, press the power button to start up the computer and then immediately press and hold the Option (⌥) key to invoke the startup disk manager.
- With the available startup disks shown, select one and then click the Up arrow to boot into your computer from the startup disk you just selected.
This is just a temporary change valid for your next boot session. After that, your computer will start up from the startup disk selected in System Preferences.
Change your startup disk for every startup
You must use System Preferences if you’d like to change your boot disk and have it remembered and used across future boot sessions until it’s changed again.
- Click the Apple menu, then choose “System Preferences”.
- In the System Preferences window, click “Startup Disk”.
- Click the lock at the bottom left to unlock the preference pane.
- Click the icon of the disk you want to use, then click “Restart”.
Your Mac will now use the selected startup disk going forward until you change it again. If you have an Apple silicon Mac, you can also set the default startup volume at boot time: with the computer shut down, press and hold the power button until you see “Loading startup options,” select a volume, press and hold the Option (⌥) key, then click “Always Use”.
Apple also provides this warning about booting from a network volume:
When selecting a network startup volume, make sure you select a network startup volume and not a network install image. Choosing a network install image reinstalls your system software and may erase the contents of your disk. A standard network volume icon appears as a globe with a folder. A network install icon appears as a globe with a downward-pointing green arrow.
You can also use the Startup Disk preferences pane to determine which disk started up your Mac by checking which startup disk is shown at the top of the preferences pane.
A note about Startup Security Utility
If you have an Intel-based Mac that’s equipped with Apple’s T2 security chip, you won’t be able to change the startup disk or boot into another operating system. Before you are able to do that, you will need to adjust your computer’s default security settings.
To change the boot volume on a Mac computer with an Apple T2 chip, you must first adjust its security settings using the Startup Security Utility. Start Security Utility is only available in macOS Recovery, which is the built-in recovery feature of your Mac.
- Turn on your Mac and hold down Command (⌘)-R immediately after you see the Apple logo.
- Select the admin user you know the password for, click “Next” and enter their password.
- In the macOS Utilities window, click the Utilities menu and choose “Startup Security Utility”.
- When asked to authenticate, click “Enter macOS Password”, then choose an administrator account and enter its password.
- Choose “Medium Security” underneath the heading “Security”.
- Click “Allow booting from external media” below the heading “External Boot”.
This is what the interface looks like.
Choosing “Medium Security” allows operating system software that’s no longer signed by Apple to run on this computer. In a nutshell, selection this option allows you to install an older version of macOS or Windows alongside your current macOS version for, say, app development or troubleshooting purposes. Allowing booting from external media lets your Mac boot from an external storage device, a USB thumb drive, an optical CD/DVD drive or other external media.
A quick note for power users: To prevent anyone from starting up your computer from a disk other than your designated startup disk, simply set a firmware password in Startup Security Utility but make sure you write it down and keep it in a safe place.
Here are the instructions for how to change the level of security used on the startup disk on your Apple silicon-powered Mac computer:
- Click the Apple menu on your Apple silicon Mac and choose the option “Shut Down”.
- Hold down the power button until “Loading startup options” appears.
- Click “Options”, then click “Continue”.
- If requested, enter the password for an administrator account.
- In the Recovery window, click the Utilities menu and choose “Startup Security Utility”.
- Select the system you want to use to set the security policy.
- If this is a FileVault disk, click “Unlock”, enter the password and then click “Unlock”.
- Now click the option “Security Policy”, then choose “Reduced Security”.
- Click “OK”.
- Restart your Mac for the changes to take effect.
Selecting “Reduced Security” will permit older versions of your Apple operating system to run on this computer, even if it’s no longer signed by Apple. As for the “Permissive Security” option, this one should only be used if you know what you’re doing because it doesn’t enforce any requirements on the bootable operating system and as such poses a potential security risk.
The whole process is also detailed in a dedicated support document on Apple’s website.