Users can let Mac boot from CD or DVD, network volume, other disk or other operating system. To do this, you can change the startup disk.
[Note] If you have a Mac equipped with an Apple T2 chip, you may need to set the new security function to change the startup disk.
Change the boot disk once
1. When the Mac or Mac equipped with Apple chip is turned off:
On Mac: Hold down the Option key when starting up the Mac.
On a Mac with an Apple chip: Press and hold the power button until you see "Loading startup options."
If you are using a Mac Mini, please wait for the system indicator to turn amber.
2. When you see the available startup disks, select one of them, and then click the up arrow (on Mac) or the "Continue" button (on Macs equipped with Apple chips).
The next time you restart your computer, it will restart from the "System Preferences" to select the disk used as the startup disk.
Change the startup disk used as a permanent startup disk
1. On a Mac, choose Apple menu 
> "System Preferences", and then click "Startup Disk."
If the lock in the lower left corner is locked 
, click the lock button to unlock the preference panel.
2. Click the icon of the disk you want to use, and then click "Restart".
[Prompt] When selecting the network boot volume, please make sure to select the network boot volume, not the network installation image. If you select a network installation image, the system software will be reinstalled and the contents of the disk will be erased. The standard network volume icon is displayed as a globe with folders. The network installation icon looks like a globe with a green downward arrow.
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