But if you use an Intel Mac with an Apple T2 Security Chip inside, the default startup security settings will prevent you from booting via removable media. Let’s check out what you can do to change that.
Step 1. Enter macOS Recovery
You can boot from an external drive on your Intel T2 Mac by modifying its startup security settings. For that, you must enter macOS Recovery. Here’s how:
Turn off your Mac. Hold down Cmd + R and press the Power button to turn it back on. Release the keys once you see the Apple logo. macOS Recovery will load shortly.
Step 2. Modify Your Security Settings
In macOS Recovery, use the Startup Settings utility to allow booting from external media:
Select Utilities > Startup Security Utility on the menu bar. Select Enter macOS Password and type in your Mac’s administrator password. Activate the radio button next to Allow booting from external or removable media and quit the Startup Security Utility.
Step 3. Boot via Your External Drive
You can now restart your Mac and boot it from an external drive. Just follow these steps:
Connect the external drive to your Mac. Then, open the Apple menu and select Restart. Immediately press and hold the Option key until you get to the boot selection screen. Pick the external drive and select Continue.
If you’re attempting to load an operating system from an external drive, you may have to disable your Mac’s Secure Boot setting. Just head back to macOS Recovery, re-open the Startup Security Utility, set Secure Boot to Medium Security or No Security, and try again.
Keep Your T2 Mac Secure
Apple Macs with T2 security chips prevent you from booting via external media due to security concerns, so you may want to revert the above changes once you’ve finished with the external drive. Even if you don’t, though, there are several other settings protecting your Mac you might want to know about.
